After counting down the Top 5 WTA tournament matches and biggest WTA upsets of 2018, our year-end review moves to the best Grand Slam clashes of the season. At No.3 is Serena Williams's comeback statement over Ashleigh Barty in the second round of Roland Garros.

Top 5 Grand Slam Matches of 2018:
No.5: Cibulkova d. Kerber, US Open
No.4: Hsieh d. Halep, Wimbledon

WHAT HAPPENED: There's been no shortage of opinions about Serena Williams's comeback from maternity leave this year - but amidst the hot takes, it's been worth taking a step back to reflect on the scale of the great champion's achievement. Returning to the game at 36 years old, barely a year removed from a complicated and traumatic childbirth involving an emergency caesarean section, Williams made it all the way back to not just one but two Grand Slam finals - an unprecedented, trailblazing athletic accomplishment.

But entering Roland Garros as a mother for the first time, there were more question marks than plaudits following Williams's tentative form in her March return, and then absence from the clay-court warm-ups. A serve-dominated first-round win over Kristyna Pliskova had settled some of those, but it was only after a thrilling 3-6, 6-3, 6-4 win over No.17 seed Ashleigh Barty in the second round that it truly felt as though the old Serena was in the house again.

Read the match report: Serena blasts past Barty in Roland Garros thriller

After a solid opening few games, Williams fell away in the first set, unable to find the court or keep up with the canny Australian, who was serving strongly and moving the ball around relentlessly. Six games passed with little reward for the former World No.1, who would win just one of them. But as she has done so many times before, Williams found what she was looking for in the nick of time: a ferocious backhand return in the second game of the second set that skidded past Barty for a clean winner and paved the way for a break back for 1-1. Game on.

To Barty's immense credit, the 22-year-old clung on. Williams's form had gone from zero to 100 following that shot, and the relatively safe tactics that Barty had settled into weren't cutting it any more. The Sydney runner-up went for her forehand and came up with wonderfully sharp angles - in essence, she forced Williams to rally, run and think. It was the perfect test - and Serena, playing the first three-set match of her comeback, passed it with aplomb, particularly impressing with her play at net and in longer points.

WHAT THEY SAID: Following the match, Barty tweeted: "A pleasure sharing the court with you, Champion." In the press conference afterwards, she pointed out that "when push came to shove, the real Serena came out - and that's one of her best assets". But the younger player's respect for her illustrious opponent didn't stop her feeling as though the outcome could have been different. "I would love to have five or six forehands again, a couple of those errors and a couple more first serves," she said ruefully. "It's disappointing, because I was well and truly in the match."

Williams, meanwhile, said that she had been playing with the correct tactics in the first set - "all the right ideas, coming to the net and hitting all my shots" - but had lacked the execution. What had got her back in the match, she asserted, was her "will to win… something I was born with, thank goodness". Williams also took the time to soak in the atmosphere in her first major back: "This time around, I was just taking [the Mexican wave] in and enjoying the moment."

Most importantly, the match was a litmus test not only of where Serena was at but where she could get to. "This is just my third tournament back and I have had a long break since my last one, so I'm probably not where I was before I left," she admitted. "But the good news is I feel like I'm definitely going to get there. And I don't want to get there, I want to get beyond there. I don't want to limit myself. That's what I want to look forward to doing."

WHAT IT MEANT: Ranked just No.451, Serena Williams would back up this win with another defeat of a seeded player, No.11 Julia Goerges, to become the lowest-ranked player to make the second week of Roland Garros in the Open Era. An arm injury would unfortunately force the American's withdrawal from the tournament in the fourth round, but she had set the tone of her comeback in earnest. By the time Wimbledon rolled around, the 23-time Slam winner was even sharper, and she would demonstrate some scintillating tennis to make the final both there and at the US Open.

It took the brilliance of Angelique Kerber and Naomi Osaka to stop the resurgent Serena in those title matches, but if this is what the legendary champion is capable of less than a year after childbirth, there is no reason not to believe that her stated goal of the all-time Slam record of 25 is well within her grasp next year.

Barty, meanwhile, had also rocketed up the rankings on returning to the sport in 2017 - and this season would prove to be one of admirable consolidation as the Australian preserved her position in the Top 20. A second career title would follow in her very next tournament in Nottingham; she broke her second-week major duck at the US Open; and she would cap the season with victory at the Zhuhai Elite Trophy to end 2018 at a career high of World No.15.