Sloane Stephens celebrated her 31st birthday with a 6-2, 6-3 win against Angelique Kerber at the Miami Open.  The 70-minute match Tuesday was the only first-round encounter between Grand Slam champions. 

"A very great day at the office," Stephens said in the postmatch interview. "I feel like I had the biggest party ever, and you guys all came out."

The result improves Stephens' record against Kerber to 6-2 overall in a rivalry dating back 12 years. The American's only losses in the series were a pair of three-set defeats -- the first as an 18-year-old in their first meeting at Indian Wells 2012 and the second at the 2021 US Open. All six of Stephens' wins have come in straight sets.

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Afterward, Stephens cited that initial loss as a factor in her ensuing dominance.

"[Kerber was] one of the first people I ever played on tour," she said. "I was up 6-2, 5-2 and I ended up losing the match. It was the hardest match I'd ever lost. After that, I just got it into my head to play her. Obviously she's such a great champion and she's had so many great results and a career people can only dream of, so to be able to play well against her is incredible."

Stephens, the 2018 Miami champion, advances to play No.19 seed Sorana Cirstea in the second round. The pair have already split two meetings in 2024, with Cirstea winning 6-3, 6-2 in the first round of Doha but Stephens turning the tables 6-0, 7-5 in the second round of Indian Wells two weeks ago. Their overall head-to-head record is all square at two wins apiece.

Kerber, whose best result in Miami was a semifinal run in 2016, was coming off a promising fourth-round showing in Indian Wells -- the first time she had won consecutive matches since returning from maternity leave in January. The former World No.1's record since her comeback now stands at 4-8.

How the match was won: Stephens, the 2017 US Open champion, played a watertight match while striking the perfect balance of consistency to aggression. She fired 26 winners and committed only eight unforced errors, frequently finding a way through Kerber with smartly timed wrong-footing shots. While Stephens's signature forehand was on song, her backhand down the line was also there for her in key moments.

No.41-ranked Stephens was also sharp in keeping hold of scoreboard momentum. Kerber raised her game at the start of the second set, finding the first break with her own trademark forehand down the line. But Stephens hit back immediately, taking advantage of Kerber's forehand inconsistency to level at 2-2.

Stephens saved one more break point in the next game to edge out to 3-2, then captured the key break of the Kerber serve for 4-2 as the German netted an overhead.