For most seeded players in the United States Open, the opening matches are a chance to work out a few wrinkles, shake off some rust and become used to the swirling winds, the warm conditions and the speed of the courts.  But Monday, many high seeds and big names instead fended off calamity in a stream of matches that turned out to be more adventurous than expected.  At the head of that list was Andy Murray, who took a two-sets-to-none lead over Robin Haase of the Netherlands, only to find himself fighting relentless muscle cramps in his legs and back. Murray, seeded eighth and two years removed from winning his first Grand Slam title here, began grabbing various muscles in the third set. He paced in front of his chair instead of sitting during changeovers and did everything he could to keep himself in the match.  He finally won, 6-3, 7-6 (6), 1-6, 7-5, as Haase seemed in nearly as much discomfort as Murray, although he was less demonstrative about it.  “There were parts of that match that weren’t particularly pretty to watch, but I’m just happy to get through,” said Murray, who has had a tough season battling back from back surgery and has not won a tournament in more than a year. The unlikely trouble hardly stopped at Murray’s match. No. 2 seed Simona Halep found herself fighting off a challenge from an American college sophomore. Jo-Wilfried Tsonga, seeded ninth and playing great tennis on hardcourts leading up to the U.S. Open, dropped a set and needed a tiebreaker to win another in a 6-3, 4-6, 7-6 (2), 6-1 victory over Juan Mónaco.  Venus Williams, 34, seeded 19th but playing one of the few touring players older than she is — Kimiko Date-Krumm, 43 — started out by spraying errors all over the court before rallying to win, 2-6, 6-3, 6-3.  That victory required Williams to overcome 36 unforced errors, 19 of them in the first set. In the third set, both players were hounded by bees, enough that Williams called for help. The trespassing bee was then ushered away by a ball boy and ball girl armed with towels.  Asked what was more troublesome, the bee or Date-Krumm, Williams laughed: “That’s a tough question. The bee was annoying, but Kimiko was tougher. She hits the ball like no one else on tour.”  No. 21 Mikhail Youzhny discovered the chaotic theme of the day the hard way, losing in four sets, 7-5, 7-6(4), 2-6, 7-6(1), to Nick Kyrgios, a 19-year-old Australian. But even though the 60th-ranked Kyrgios is unseeded at the Open, he is not an unknown quantity, having knocked Rafael Nadal out of Wimbledon. Kyrgios takes full advantage of the energy of youth, relentlessly pushing the pace of the match.  Kyrgios snatched the first two sets before wobbling. He became so frustrated he earned three code violations, one for hitting a ball nearly out of Court 17.  “It just comes from having high expectations most of the time,” said Kyrgios, who would have defaulted the match with one more code violation. “I have been an emotional player most of my career. Maybe I will be able to manage it in the future.”  When Youzhny looked as if he might send the match to a fifth set, Kyrgios came back from a breakdown in the fourth to grab victory in a tiebreaker.  “I was struggling a little bit about that two-and-a-half-hour mark, but I knew that if I hung in I would get that second wind where I could start playing good tennis again,” Kyrgios said.  The same could be said for Halep, who seemed to be on the verge of coming unglued in the first set of her 6-7 (2), 6-1, 6-2 victory over Danielle Rose Collins.  Halep could have been excused for overlooking Collins, who was playing in her first Open, as the beneficiary of a wild card she earned with a surprise victory in the N.C.A.A. tournament. Collins, the No. 32 seed, marched through the draw to become the first women’s singles champion from the University of Virginia.  Collins battled Halep into a first-set tiebreaker, where Halep seemed to lose her composure as well as the set. After dumping several balls into the net in the tiebreaker, Halep took big swipes with her racket, barely missing smashing it into the court.  “It’s really difficult to be second seeded here,” Halep said. “It’s my first time and my best ranking and the best moment of my life, but it is difficult. There is a lot of pressure on me. People say I should win and I can win. I want to take match by match and see how far I can go in this tournament.”  For Halep, a loss would have marred an otherwise spectacular year. She started with a run to the quarterfinals at the Australian Open; a trip to the final of the French Open, where she lost to Maria Sharapova; and a semifinal appearance at Wimbledon, where she lost to Eugenie Bouchard.  Halep used her first break opportunity in the second set to swing the match in her favor. She pounced on a few short balls hit by Collins — the kind that unnerved Halep in the first set — and pounded them for clear winners. She needed only 33 minutes to win the second set, followed by a victory in the third.  No. 6 Angelique Kerber also needed three sets and more than two hours to win her first-round match against unseeded Ksenia Pervak, 6-2, 3-6, 7-5. Even third-seeded Stan Wawrinka’s straight-set victory was far from straightforward. Wawrinka got only 47 percent of his first serves in and converted just 4 of 12 break-point chances against 75th-ranked Jiri Vesely before winning, 6-2, 7-6 (6), 7-6 (3).  “It was a really tough match,” said Wawrinka, the Australian Open champion this year. “The first round here, it’s never easy.”  But some had it easier than others. No. 5 Milos Raonic defeated Taro Daniel, 6-3, 6-2, 7-6 (1). Agnieszka Radwanska, the No. 4 seed in the women’s draw, advanced past Sharon Fichman of Canada, 6-1, 6-0, in 47 minutes. No. 21 Sloane Stephens steamrollered Annika Beck of Germany, 6-0, 6-3, in 61 minutes. Kurumi Nara of Japan, the No. 31 seed, needed 59 minutes to rout Aleksandra Wozniak of Canada, 6-2, 6-1.  In addition to Youzhny, other seeds to lose during the day were No. 24 Julien Benneteau, who fell to his fellow Frenchman Benoit Paire, 7-6 (4), 5-7, 6-4, 4-6, 6-4, and Garbiñe Muguruza, the No. 25 seed in the women’s draw, who was eliminated by the qualifier Mijana Lucic-Baroni, 6-3, 7-6 (4).  An earlier version of this article misstated Angelique Kerber’s seeding. She is the No. 6 seed, not the No. 5.  A version of this article appears in print on August 26, 2014, on page B11 of the New York edition with the headline: First Session Presents Challenges and Annoyances for Seeded Players. Order Reprints|Today's Paper|Subscribe
Andy Murray survived severe cramping to win, Simona Halep needed three sets to advance and Venus Williams overcame errors and a pesky bee, but No. 21 Mikhail Youzhny was upset by Nick Kyrgios.