Three-time major champions Andy Murray and Stan Wawrinka win opening-round matches

On the first day of the two-week U.S. Open, of course, it’s all unhatched chickens. Nothing to really count yet.

Three-time major-tournament champion Andy Murray won his opening match in four sets against Australian James Duckworth but acknowledged that there were “many, many things that I would have wanted to change” in recent months “to be considered a contender here.”

Three-time major-tournament champion Stan Wawrinka won his opening match, technically an upset because the currently 101st-ranked Wawrinka took out No. 8 seed Grigor Dimitrov in straight sets, but said he is “still far away to put myself” as a title threat.

Milos Raonic, the world’s No. 3 player just two years ago but now a more humble 25th, won a four-setter over 160th-ranked Argentine Carlos Berlocq but evaluated his situation as mostly having “been able to stay relatively healthy” lately.

The featured night matches included two other players who have had physical problems in their careers but also reached the second round. Top-seeded Rafael Nadal advanced, 6-3, 3-4, ret., when a limping David Ferrer was unable to continue, and No. 3 seed Juan Martin del Potro topped Donald Young in straight sets.

On the pie chart of potential success, the percentages tip to caution over expectation. Mostly for medical reasons. Murray, on the mend from hip surgery, is playing a Slam event for the first time in 14 months. Wawrinka, after winning the Open two years ago, is working with a post-surgical knee. Raonic has muddled through shoulder and knee problems.

In fact, this Open marks the first Slam in which the biggest names in men’s tennis—Roger Federer, Novak Djokovic, del Potro, Nadal, Murray and Wawrinka—all are whole enough to be in the same field. Djokovic had an operation on his elbow, del Potro has had several procedures, Nadal seemed to have been hurt from head to toe at some point.

Murray, whose long absence has left him ranked 378th, was asked if he thought tennis has become as dangerous as boxing. A case in point was that his opponent, Duckworth, has had five operations.

“I don’t think so,” Murray said. “But it’s difficult in tennis just now, because you’ve got a lot of the top players that are playing longer and competing at the highest level for longer, and there has been periods where a lot of the top players have been out with significant injuries and surgeries and stuff.

“You know, it’s a physically very challenging game.”

There was some good news for U.S. tennis yesterday when No. 11 John Isner defeated wild card Bradley Klahn in straight sets; Taylor Fritz, ranked 70th, squeaked out a five-setter over 46th-ranked German Mischa Zverev, who had enjoyed a nice run at last year’s Open; and 18th seed Jack Sock, who had been struggling mightily of late with a bad hip, knocked off 118th-ranked Guido Andreozzi of Argentina in three sets.

“I’ll be honest with you guys,” Sock said. “When things aren’t going well, it honestly feels more like the end of the world than giving an appreciation” for the sport.

So hold the cart until the horses can get going. Sam Querrey, who had risen to No. 12 just a year ago but now is 35th, on Monday was done in by a cramp that attacked his forearm and hand in the fourth set. Down two sets to one, he retired.