2017 US Open champion Sloane Stephens and No.9 seed Garbiñe Muguruza of Spain came through extremely difficult first-round draws as the 2021 US Open got underway on Monday.

Stephens had to triumph in a rematch of the 2017 US Open final just to win her first-round clash this year. The former titlist edged her good friend and fellow American Madison Keys, 6-3, 1-6, 7-6(7), in the first match on Arthur Ashe Stadium of the fortnight.

The former Top 10 players have seen their rankings slide to World No.42 (Keys) and World No.66 (Stephens), but their talents were on full display in a tense, two-hour and 10-minute tussle, especially in an evenly-matched third set which came down to the wire.

Stat corner: Stephens led the rivalry by four wins to two coming into the match, and had won both of their meetings in Grand Slam tournaments (also in the 2018 Roland Garros semifinals, after which Stephens reached the second of her two major finals).

Keys was the aggressor for the most part, with 36 winners, three times the total from Stephens's racquet, with the ratio particularly in her favor during the second set. But Keys also had 37 unforced errors to Stephens's 25, and those miscues sealed her fate in the decisive tiebreak.

Critical junctures: An early break for Stephens was retained throughout the opening frame, and she claimed a second break to notch the one-set lead by the same score she had won the first set of their US Open final four years ago.

However, unlike that final, Keys stormed back with gusto in the second set. The power game from Keys clicked into place as she zipped to a 4-0 lead in that set, then eased through the remainder. Keys had 11 winners to just three unforced errors in the second set.

In the final set, Stephens garnered two break points at 4-4, but Keys used incredible forward-thinking aggression to hold on for 5-4. At 5-5, Stephens converted her fourth break point of the game to serve for the match, but Keys struck back immediately to queue up the breaker.

In the tiebreak, the players jockeyed back and forth with sturdy groundstrokes, and Stephens saw two match points at 6-5 and 7-6 slip away. But Stephens reached a third match point after a netted forehand by Keys, and she took that chance after a Keys backhand flew wide.

Quotes from the players: "Playing Madison is always difficult," Stephens said, after the match. "We're friends and then obviously Americans playing at the US Open is never easy. And then of course we played here in the final in 2017. So there was a lot of stuff surrounding the match just because it's something that we're familiar with, and I think a lot of people wanted to see."

"I think today we both went out and did our best and we played a really great match," Stephens added. "It's just unfortunate that someone has to win and someone has to lose."

Meanwhile, Keys, in her post-match press conference said, "I actually think it's the best I have played in a while, but I also think it's the best she's played in a while. Just a really tough first round, and, I mean, I left it all out there. I did what I could, but it wasn't good enough."

"There is just a lot that I can actually take from the match and learn from, but also be really proud of for the rest of the season," Keys continued.

Next up: Things won't get any easier for Stephens in the second round. She will next face No.21 seed and fellow American Coco Gauff, who also won a three-set first-round tussle against Magda Linette of Poland, a semifinalist last week in Cleveland.

Photo by Darren Carroll/USTA

Muguruza fends off Vekic challenge

Just minutes before Stephens won, Muguruza eked past Donna Vekic of Croatia, 7-6(4), 7-6(5) in the first match on Louis Armstrong Stadium this year.

Former World No.1 Muguruza had to stare down a huge test from 57th-ranked Vekic, a former Top 20 player who reached the US Open quarterfinals just two years ago. The pair had split their two previous meetings.

But Muguruza was able to rise to the challenge, coming back from an early break down in the opening set and staving off a second-set comeback by Vekic to notch the hard-fought win after two hours and 18 minutes of play.

Stat corner: Two-time Grand Slam champion Muguruza (2016 Roland Garros, 2017 Wimbledon) is still looking for her US Open breakthrough, with a single round-of-16 appearance in 2017 being her career-best showing in Flushing Meadows.

Muguruza was pushed from beginning to end by 2019 US Open quarterfinalist Vekic, with Muguruza winning a whisker more points off of the first service, 77 percent for the victor to 76 percent by the Croat.

The hard-hitting clash finished with Muguruza hitting 29 winners to 26 unforced errors, while Vekic fired an equally impressive 36 winners to 30 unforced errors.

Key moments: After falling behind a break at 4-2, Muguruza struck back immediately to pull level in the set once more. In a closely-contested first-set tiebreak, Muguruza took charge by cracking open a rally with an error-forcing backhand to lead 6-4, before converting her first set point.

A 3-0 lead in the second set for Muguruza disappeared when, serving for the match at 5-3, Vekic's return game amped up, and the Croat dragged the affair into another tiebreak.

But in the breaker, it was the Muguruza return which dominated, as she slammed two screaming winners with that shot to keep herself in front. The forehand from both players collected them points in the latter stages of the tiebreak, with Muguruza taking those rallies in two of the last three points to seal victory.

The winner's thoughts: "It was a very tough first round," Muguruza told the press, after her win. "Having to play [Vekic] in the first round was difficult, and I could see it on court. I knew it was two close sets that I was happy to close in the tiebreak, which can go any way at that point."

"It's just a Slam that historically is not my strongest," Muguruza added. "I was so pumped to go out there. And I saw the time when we were playing in the second set: it was, like two hours-something, and we were still in the second set. I was like, 'Okay, it's a good moment to close the match!'"

Looking ahead: Muguruza will next face Andrea Petkovic of Germany, who defeated Irina-Camelia Begu of Romania, 6-2, 7-6(3). 

Former Top 10 player Petkovic reached her first final in six years in Hamburg earlier this summer, and went one better mere weeks later in Cluj-Napoca, where she won her first WTA singles title since 2015.