Novak Djokovic's neck felt much better, and his tennis looked much better, in a 6-2, 6-4 victory over unseeded American Tennys Sandgren at the Western & Southern Open that improved the No. 1-ranked man to 20-0 in 2020.
"Actually, I'm pleasantly surprised with the way I recovered and felt today, just overall, physically, but also with the neck, specifically, because that was a little bit of a concern," said Djokovic, who will be eyeing his 18th Grand Slam title when the US Open begins next week.
"Going back four, five days, I did struggle quite a lot."
This is the first ATP tournament in more than five months because of the COVID-19 pandemic, and while Djokovic was treated by a trainer and played sluggishly in his opening match Monday, he took control from the outset against Sandgren and saved all four break points he faced.
Djokovic tested positive for the novel coronavirus in June after organising a series of exhibition matches in Serbia and Croatia, where fans were allowed and masks and social distancing were not mandated.
He has won five of the past seven Grand Slam tournaments, including at the Australian Open in February. His winning streak is the longest to open a season since he began 41-0 in 2011, which is the best start for a man since at least 1990.
Djokovic was asked about the idea of finishing this unusual and truncated year undefeated.
"Look, anything is possible. ... I don't want to count that out, I mean, especially because of the fact that we don't know how the post-US tour season is going to look like, whether we are going to play, whether there is going to be another lockdown in Europe or not. We are hoping not," he said.
"Right now, it's not something I'm thinking about. It's not my goal, actually, to go unbeaten, but I wouldn't complain if I do."
Djokovic will face 34th-ranked Jan-Lennard Struff in the quarterfinals. The other quarterfinal in the top half of the draw will be defending champion Daniil Medvedev against No. 8 seed Roberto Bautista Agut.
The No. 3-seeded Medvedev's 2019 title at the Western & Southern Open was part of a stretch in which he reached the finals at six consecutive tournaments, including a runner-up finish to Rafael Nadal at the US Open.
Reilly Opelka, a 6-foot-11 American who is ranked 39th, delivered 19 aces and knocked off 2019 U.S. Open semifinalist Matteo Berrettini 6-3, 7-6 (4). Opelka next meets No. 4 seed Stefanos Tsitsipas, whose 7-6 (2), 7-6 (4) win over No. 16 John Isner was interrupted by a rain delay of nearly 1 1/2 hours late in the first set.
Also interrupted by the weather was three-time Grand Slam champion Andy Murray's 6-2, 6-2 loss to 2016 Wimbledon runner-up Milos Raonic, who has held all 29 games he's served so far in the tournament.
"It was poor. Didn't play well. It was not a good day," said Murray, who hadn't competed since November because of a pelvic injury and is playing on a metal hip after two operations on that joint.
"The positives are that I got three matches in. Physically, I pulled up OK."
That was followed by Serena Williams against Maria Sakkari in the day's last match.
Women's quarterfinal matchups set earlier in the day were two-time Grand Slam champion Naomi Osaka against Anett Kontaveit, former No. 1 Victoria Azarenka against Ons Jabeur, and 83rd-ranked American qualifier Jessica Pegula against No. 14 Elise Mertens. Pegula beat No. 5 seed Aryna Sabalenka 6-2, 2-6, 6-3.