With the US Open's first round coming to a close, both surprise performances and expected wins headlined the season's final Grand Slam heading into today's second round.

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Naomi Osaka pulls off stunning upset with US Open win

Looking decidedly dangerous, 2020 US Open champ Naomi Osaka — a wild card entry at 88th in the world — beat No. 10 Jeļena Ostapenko in straight sets on Tuesday.

After stepping away for mental health reasons and the birth of her daughter, yesterday marked Osaka’s first top-10 win in over four years.

"Last year, I was watching Coco play, and I so badly wanted to step on these courts again and I didn’t know if I could," an emotional Osaka told reporters after the victory. "Just to win this match and to be in this atmosphere means so much to me."

Britain's Emma Raducanu reacts during her first-round US Open loss on Tuesday
Emma Raducanu's first-round loss on Tuesday continued her US Open losing streak since her surprise 2021 tournament win. (Robert Prange/Getty Images)

Other past US Open champions see mixed results

Joining Osaka in the second round are fellow US Open winners Iga Świątek (2022) and Coco Gauff (2023). No. 3 Gauff aced her first match 6-2, 6-0 on Monday, but No. 1 Świątek faced a tougher challenge from Russian Kamilla Rakhimova on Tuesday.

The Polish phenom made 41 unforced errors, coming dangerously close to a forced third set before a tiebreaker allowed Świątek to continue her hunt for a sixth Grand Slam title.

Other past US Open champs weren’t so lucky, with 2019's Bianca Andreescu and 2021's Emma Raducanu joining 2017's Sloane Stephens on the ousted list.

No. 11 Danielle Collins tosses a tennis ball up for a serve in her first-round US Open loss on Tuesday
Retiring US tennis star Danielle Collins fell in US Open's first round — her final Grand Slam — on Tuesday. (TIMOTHY A. CLARY/AFP via Getty Images)

Retiring Danielle Collins exits final Grand Slam singles tournament

While most of the 32 seeded singles players survived round one, US star Danielle Collins's run ended on Tuesday. Coming off a solid fourth-round Wimbledon exit, the world No. 11 fell to No. 49 Caroline Dolehide 1-6, 7-5, 6-4, despite defeating the fellow US pro in five of their six previous meetings. 

Collins, who announced her plan to retire after this season in January, suffered an abdominal injury at the Olympics that saw her miss the Toronto and Cincinnati US Open tune-ups.

Ash Barty continued to roll on Thursday, breezing past Madison Keys 6-1, 6-3 to reach the final of the Australian Open. She’s the first home player to reach the women’s final since Wendy Turnbull in 1980.

With the win, Barty’s hopes of becoming the first women’s home champion since Chris O’Neil in 1978 are still alive.

Having dropped just 21 games in six matches, Barty recorded the fewest games lost en route to a Grand Slam title match since Serena Williams dropped 16 en route to the 2013 US Open final. It’s also tied for fourth-lowest this century: Williams dropped 19 at the 2012 US Open, sister Venus dropped 20 at Wimbledon in 2009 and Serena also dropped 21 at the 2013 French Open.

Throughout the 62 minute match, Barty racked up 20 winners to 13 unforced errors. Keys, meanwhile, had only eight winners to 24 unforced errors.

“It’s tough,” Keys said of Barty’s play after the match. “It sucks. She’s just playing incredibly well. I mean, you have a game plan in your head, but she’s just executing everything so well.”

The Australian will next take on No. 27 American Danielle Collins, who upset No. 7 Iga Swiatek 6-4, 6-1 to reach her first Grand Slam final. It was Collins’ seventh career top 10 win.

When asked about Collins, Barty called her “one of the most fierce competitors out here.”

“She loves to get in your face and loves to really take it on,” Barty said. “It’s going to be a challenge for me to try and neutralize as best that I can, but it is certainly nice to see her back out here playing her best stuff.”

While Barty leads the head-to-head against Collins 3-1, the American hasn’t lost a complete match since Indian Wells last October, marking a streak of 11-straight wins. She had to retire to Alison Riske in the Linz Open semifinals in November.

The 28-year-old slammed home 27 winners and only 13 unforced errors on Thursday. Her aggressive approach to the game was no match for Swiatek, who said as much after the match.

“I was prepared for her playing aggressive game, but I think that was the fastest ball I have ever played against on a match,” Swiatek said. “For sure in practices I have hit maybe the same speed, but on matches it’s different because players don’t want to take that much risk. But it seemed for her that it wasn’t even risky because she was playing it with control.

“So I am impressed, and huge respect to her because she’s playing a great game. I’m just curious how it’s gonna look like on the final, and I’m gonna for sure be watching and learning.”