Welcome back to Clay Chronicles, where wtatennis.com will take a look back at some of the most memorable matches from the clay seasons of the past five years. After recapping Charleston's classics and Stuttgart's standards, our retrospective now heads to Madrid, Spain to recount some of the best matches from recent editions of the Mutua Madrid Open. Kicking things off is a heavyweight third-round clash from 2015 as World No.1 Serena Williams battled to hold off former World No.1 Victoria Azarenka, hot on the comeback trail.

HOW THEY GOT THERE: Even by Serena Williams's lofty standards, the American was particularly untouchable as she entered the 2015 clay season. Williams had captured her 18th Grand Slam trophy at the previous year's US Open, a milestone that tied her with Chris Evert and Martina Navratilova at fourth on the all-time list of major titles; and if her journey there had required her to overcome a number of nervy failed attempts in 2014, achieving it had unleashed her.

Williams's fifth WTA Finals title, and third in a row, had followed the US Open, and there had been no let-up in 2015 as she racked up her 19th Grand Slam trophy at the Australian Open and completed a second hat-trick of titles in Miami. Transitioning to clay had revealed some rare vulnerability: in the previous fortnight's Fed Cup play-off tie against Italy in Brindisi, Williams had needed to come from a set and a break down to quell Sara Errani 4-6, 7-6(3), 6-3, and she had followed that by losing her first ever Fed Cup rubber in the deciding doubles, partnering Alison Riske and falling 6-0, 6-3 to Errani and Flavia Pennetta. But back on the WTA Tour, that weekend seemed like a brief blip: Williams was majestic in her first two matches in Madrid, where she had won the title in 2012 and 2013, conceding just five games in total as she dismissed Madison Brengle 6-0, 6-1, and Sloane Stephens 6-4, 6-0, extending her winning streak to 25 in her 119th consecutive week at World No.1.

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Meanwhile, Azarenka - Williams's predecessor at the summit - was battling to regain the peak form that saw her reach four major finals, winning two, in 2012 and 2013. A foot injury had repeatedly set the Belarusian back in 2014, causing her to miss that year's clay season; a knee injury added to her woes during the hardcourt swing, and after a second-round loss in Tokyo to Ana Ivanovic in September, Azarenka shut her year down in a bid to heal her body properly.

The 26-year-old's return was a somewhat fitful one. There were matches in which Azarenka seemed ready to rejoin the elite - straight-sets defeats of Stephens and Caroline Wozniacki at the Australian Open, and a run to the Doha final that included solid wins over Angelique Kerber, Elina Svitolina, Wozniacki and Venus Williams. Having fallen to World No.50 in February, she had managed to clamber back up to World No.31 by the time Madrid rolled around.

Gallery: Madrid Memories 2012: Serena's brilliance in blue

But for every positive sign, there seemed to be a step back as Azarenka was unable to translate those performances into a sustained run of form. Both of her best 2015 tournaments had ended in a loss to a player she had hitherto dominated - Dominika Cibulkova in the fourth round of the Australian Open and Lucie Safarova in the Doha final - while elsewhere, Azarenka squandered two match points to fall to Karolina Pliskova in the first round of Brisbane, was dismissed 6-4, 6-3 by Maria Sharapova in the third round of Indian Wells, and showed her vulnerability on big points in the fourth round of Miami, where Flavia Pennetta edged her out in two tiebreaks.

In Madrid, Azarenka had followed a 6-3, 7-5 upset of No.16 seed Venus Williams by easing past Ajla Tomljanovic 6-3, 6-3 to set up the clash against Serena, whom she had not faced for 16 months. And while, in addition to the pair's contrasting forms, a 14-3 head-to-head heavily tilted in Serena's favor - including their two most recent encounters in the 2013 US Open and 2014 Brisbane finals - would stack the odds even further against Azarenka, the latter could still argue that after half a decade, she was finally redressing the rivalry somewhat: since the start of 2013, she had won two of their five meetings.

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WHAT HAPPENED: The heavyweight tone of the contest was set by an opening act in which both players refused to give an inch. Dictating with serve-dominated, first-strike tennis that belied the clay surface, neither would face so much as one break point during the first set, repeatedly hitting corners and lines to rack up service winners and one-two punches.

A tiebreak was inevitable, and initially Azarenka proved sharper, moving out to a quick 5-1 lead. But with Williams's back to the wall, the top seed's ability to erase a seemingly insurmountable deficit in a couple of lethal swings came through once again. Teeing off on the Azarenka serve for clean return winners, Williams reeled off six straight points to snatch the set clean out of her opponent's hands.

The American showed no sign of letting up as the second set got under way. Azarenka's ability to hold her at bay had evaporated - instead, when the 2011-12 Madrid runner-up stepped up to the line during this period, it was with the very real threat of having her best deliveries sent back with twice the ferocity as Williams swatted her returns into the corners. Consequently, it was the 2012-13 Madrid champion who captured the first break of the match and, standing at 3-2, 40-15, seemed to be mere games from reprising her victory over Azarenka in the 2012 final.

This time, though, it was the Belarusian's turn to dish out a taste of Williams's own medicine. A sweetly struck clean backhand return winner was the start of the turnaround as a seemingly-outgunned Azarenka raised her game to seize momentum back. That return paved the way to the break back - and to 16 of the next 19 points as she reeled off four straight games to take the set. Suddenly, Williams was slapping the ball with less accuracy; a double fault conceded a second break, and a wayward dropshot down set point enabled Azarenka to level the match.

Madrid: Williams vs Azarenka

If a rattled Williams seemed to have lost her focus, it didn't last for long. The start of the deciding set saw another emphatic momentum swing as the 33-year-old, rediscovering her easy lethality - and another handful of return winners - took 12 of the first 14 points, and a healthy 3-0 lead. But Azarenka still couldn't be quelled: unfazed by the passages of play in which she was all but shut out, the two-time Australian Open champion buckled down to gradually peg Williams back.

Ever since the first-set tiebreak, Azarenka had been chasing Williams from behind. Serving down 4-5, she fended off a match point in style with a spectacular forehand into the corner - and this, briefly, seemed to be the turning point her efforts had patiently gone towards. Frustrated at the missed chance, Williams delivered one of her worst service games of the day at the worst possible opportunity, falling behind 5-6 with a shanked forehand. Azarenka advanced to triple match point at 40-0, on the brink of her biggest win in two years - but there was still time for another plot twist.

A forehand winner and a booming backhand return from Williams saved the first two match points - and then disaster struck for Azarenka with a double fault. Another would concede the game - and for all the fight she had displayed over two hours and 44 minutes, the 26-year-old was unable to recover in time to even make the deciding tiebreak competitive.

In the blink of an eye, Williams had gone from the verge of defeat to the joy of victory, winning 12 of the last 13 points to seal a 7-6(5), 3-6, 7-6(1) triumph in two hours and 44 minutes after racking up 13 aces and 49 winners to five double faults and 53 unforced errors.

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WHAT THEY SAID: "I've done a lot of work on myself to be able to reflect a little bit better on good and bad things, and not just on the court," Azarenka mused. As a result of this "self-work", despite the gutting nature of the defeat, she was determined to take the positives from the match and walk away with no regrets.

"Really on this last match point, the matter of winning or losing was less than one centimeter," Azarenka pointed out, referring to the bold second serve that had just ended up as a double fault. "Looking back at it, I'm not going to regret it - because I went for my shot. If I [hadn't], I would probably be sitting here saying, Should I have gone or not? I did, and it didn't go in by a centimeter. Next time I'm going to do the same, and hopefully it will land that one centimeter in."

Zooming out to the larger picture, Azarenka declared herself pleased with the arc of her comeback: "I feel I've been on the right track for a while. Just the process is that of improvement. I feel like with every tournament I do get better and better." In this match, she assessed her form as "a pretty high level" with only one dissatisfying aspect: "I think the one negative part about today I can take is the result."

Read more: Azarenka on facing Serena: 'She's my favorite person to play against'

Williams was less happy with her level - " I missed so many easy shots... it was just a little frustrating for me, I know I could have played and made some better shots" - and paid tribute to Azarenka's form, in particular her serve. "She did some new things... I felt like she was really able to hit a lot of aces and do a lot of things like that," Williams said. On her opponent's near-miss on match point, the American champion also elucidated on what she would have done differently: "She almost hit an ace and just missed it by not even three centimeters," recalled Williams. "So I thought, Wow, she shouldn't challenge that. If she challenges she's going to hit a double fault. Sure enough, she did."

But despite her initial disbelief - "I really ended up winning and I don't know how" - Williams was also able to expand on her mindset with her back to the wall. "At that point you have nothing to lose - you just kind of play and hopefully go down with dignity," she reflected. "I thought, OK, I'm down 0‑40. I have a 2% chance I'm going to win. I had a match point earlier in the match, so I thought, At least win one, that way it'll kind of seem like we're even because we both won a match point. Only difference is she had three in a row and I didn't. Only wanted to win one, and from that point just kept going literally one point at time."

That approach paid off with a win Williams described as "intense" - but already, her focus was on the future. "I just really have to... go over why I was in this situation, figure out what I can do to be better for my next match," she stated firmly. "Hopefully not be in this situation, but if I am, hopefully I can come through it again." And, ominously for Azarenka, Williams signalled that she wouldn't forget this match. "Next time I'll know what to expect," she said. "I'll be able to play better, and then I'll be better."

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WHAT IT MEANT: Williams would go on to the semifinals, but there ran into the juggernaut of a peaking Petra Kvitova, who snapped the World No.1's 27-match winning streak 6-2, 6-3. Nonetheless, Williams would bounce back from that - and the elbow injury that cut short her Rome campaign the following week - to capture her third Roland Garros title in 2015, a run characterized by more three-set battles as she fought through illness over the fortnight.

Indeed, the 2015 season would be of immense significance in cementing Williams's legacy of greatness: the Roland Garros crown was followed in swift succession by the Wimbledon title, her 21st Slam and one that sealed a second 'Serena Slam', 13 years after the first time Williams had held all four major trophies simultaneously.

Williams would end the year with an astounding 53-3 win-loss record - her 95% winning percentage remains the second-highest of her career - and, for the fifth time, the World No.1 ranking. The last loss would be one of her most painful, though: in the US Open semifinals, two wins from the first Calendar Year Grand Slam since Stefanie Graf accomplished the feat in 1988, Williams would fall from a set up to the unseeded Roberta Vinci.

Gallery: Miami and Indian Wells: Sunshine Double champions

Azarenka's comeback, meanwhile, would continue to progress in fits and starts. Some of the best tennis the former World No.1 played in 2015 would be against Williams - but twice again she would suffer heartbreaking losses, falling 3-6, 6-4, 6-2 in the third round of Roland Garros and, in another top-quality clash, 3-6, 6-2, 6-3 in the Wimbledon quarterfinals.

As the year drew on, Azarenka remained unable to translate patches of form that garnered her wins over Petra Kvitova (in Montréal), Caroline Wozniacki (in Cincinnati) and Angelique Kerber (at the US Open) into titles, falling to Sara Errani in Canada and Simona Halep in the quarterfinals at Flushing Meadows. Even more disappointingly, Azarenka's body still refused to cooperate: a thigh injury forced her to retire while leading Anastasia Pavlyuchenkova 6-1, 0-3 in the quarterfinals, and its recurrence ended her Asian swing prematurely after retiring against Johanna Konta in the third round of Wuhan.

Persistence paid off for Azarenka, though, whose revival finally came to fruition at the start of 2016, when titles in Brisbane, Indian Wells and Miami - the latter two of which sealed just the fourth Sunshine Double run in WTA history - rocketed her back into the Top 5.

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