Gauff's Serve, Rybakina's Return: The Semifinal That Toronto Already Rehearsed

The US Open semifinals arrive on Thursday night in New York, and this one carries a peculiar kind of symmetry. Coco Gauff, the No. 4 seed, has not lost a match since Elena Rybakina, the No. 2 seed, took her apart in the Toronto semifinal — she went on to win Cincinnati and has moved through four rounds here without dropping a set. Rybakina, meanwhile, arrived in New York barely able to practise after retiring in Cincinnati with a left-ankle problem, and will leave the tournament as world No. 1 whatever happens on Thursday. Both survived three-set quarterfinals on Wednesday. Neither played anything close to her best tennis to do it, and that is exactly what makes the evening interesting.

Gauff Has Learned to Win Without Her Best Tennis

The quarterfinal against Mirra Andreeva was, by Gauff's own description, probably her worst serving match of the season. Andreeva kept feeding the ball into the forehand, drawing short replies, and the first set slipped away before Gauff had begun to feel the ball at all. Then came the second-set tie-break, a 39-shot rally at 4-3 that she closed with a drop shot, and two match points saved. From the start of the decider she was the only player on court moving freely.

That is the pattern of her whole summer. In Cincinnati she was overwhelmed by Liudmila Samsonova in an opening set, improved after a rain delay and never looked back; Jessica Pegula called her "like a backboard" in the final. Against Iva Jovic in the fourth round here she was broken immediately and then took control for long stretches. Gauff has said she is better now at leaving missed chances "in the past" and trusting that another opening will come — and after Andreeva she put it more plainly still: "The game may not always show up, but I can control the belief in myself."

The worry is that the two things that failed her on Wednesday — the serve and the forehand — are precisely the two things Rybakina is built to attack. The serve reconstruction with biomechanics specialist Gavin MacMillan, alongside Jean-Christophe Faurel, is a work in progress rather than a finished product. The encouraging detail is that Gauff no longer abandons the motion after a handful of misses; the team distinguishes between the old structural misses and the honest double faults that come from committing. No injuries reported, but she played later than Rybakina on Wednesday and has the shorter turnaround.

From a Damaged Ankle to the Top of the Rankings

Rybakina's fortnight is the better story of recovery. She left Cincinnati unable to push off on her serve, received treatment and retired, then came to New York after a week without tennis and with her gym work restricted. The ankle was assessed day by day. She has since played five matches without a recurrence, without treatment on court and without any visible limitation in movement.

The tennis got better as the ankle held. Against Naomi Osaka in the fourth round she produced her cleanest performance of the tournament — controlling the first strike, denying an elite ball-striker any settled attacking rhythm, and doing it without the emergency comeback their chaotic Toronto meeting had required. The quarterfinal against Zheng Qinwen was messier: her first full midday match here, and she admitted she was bothered by the sun, the shadows and her own thinking. "It was definitely a battle inside me, but I pushed all the negative thoughts away."

What she did at 3-4 in the decider matters more than how she looked before it. Facing break point, she moved forward, survived, then won six straight points, broke and served it out. That is the same late simplification that carried her through the Australian Open final. She reaches the top of the rankings on Monday regardless, and she has treated it with characteristic flatness: "It's just a number right now." This is her first US Open semifinal, at the major that has always suited her least.

The Match Turns on One Question: Can Rybakina Get Into the Second Serve?

Toronto is the map. Gauff won the opening set there by serving well and making Rybakina play through her defence. Early in the second, Rybakina started standing in and driving returns flat through the middle and at Gauff's feet; the service rhythm broke down, the double faults arrived, and Rybakina controlled the rest. She later said she sensed Gauff "started to feel a bit of pressure" after those returns. Rybakina does not need clean return winners here — deep, heavy returns that deny Gauff time on the first forehand are enough.

The counter-plan is Gauff's legs and her backhand. She wants Rybakina hitting one extra difficult ball, after lateral movement, after braking and changing direction — and Andreeva's blueprint of hammering the Gauff forehand only works if Rybakina resists the temptation to go for the lines too early. Purely defensive tennis will not do it: if Gauff retrieves but leaves the ball central and short, Rybakina keeps attacking for free. Gauff's forehand does not have to win the match, only to hold enough depth and height to stop every second ball being a target. Rybakina's backhand down the line is the tool that opens the forehand without much initial risk.

Conditions favour Rybakina in one specific way and Gauff in another. The night session removes the sun and shadow that unsettled her against Zheng, and Rybakina completed her quarterfinal several hours earlier on Wednesday. Against that, Arthur Ashe will be loudly for Gauff, and she has said New York's energy makes her want to perform. The ankle is unlikely to be truly tested until she is pulled wide and asked to plant repeatedly; whether it is entirely symptom-free after another long match is unverified.

So watch the small things. Whether Gauff commits to a second serve after an early miss. Whether Rybakina goes through the middle before she goes for angles. Which player handles the first failed attempt to serve out a set. And above all, whether Gauff can get through the opening games of the second set without the Toronto momentum swing repeating itself — because both of these players spent Wednesday proving that no lead in this tournament is safe.