NEW YORK (AP) — Excited to be seeing an old pal for the first time in a while, the U.S. Open spectators dotting the mostly empty stands in Arthur Ashe Stadium called out to Kim Clijsters as she stepped on the court that means so much to her.

“Come on, Kim!” yelled one fan. And then another. And yet another. “Hey, Kim!” someone else shouted.

Monday morning’s setting was a familiar one for Clijsters, whose lone Grand Slam championship came at Flushing Meadows on Sept. 10, 2005. That was the last time she played at the U.S. Open, and while the site was the same, the circumstances and the stakes were oh-so-different.

Clijsters’ 6-1, 6-1 victory over 79th-ranked Viktoriya Kutuzova of Ukraine on Monday came in the first round, the 26-year-old Belgian’s first Grand Slam match since January 2007. In the intervening two-plus years, Clijsters retired, got married and, in May 2008, gave birth to a daughter. Once No. 1, she came to the U.S. Open unranked and needed a wild-card invitation from the U.S. Tennis Association.

“Little more nervous than usual. It’s a very special court to me, but I really enjoyed it,” Clijsters said. “I felt really good out there.”

She came back this month at two hard-court tuneup tournaments, going 5-2. Clijsters made that 6-2 on a day of many happy returns at the U.S. Open. Defending champions Roger Federer and Serena Williams won, too, and Andre Agassi came back to the site of the final match of his career in 2006, participating in an opening-night ceremony.

By beating 18-year-old NCAA champion Devin Britton of Jackson, Miss., 6-1, 6-3, 7-5, Federer ran his winning streak to 35 matches at the tournament and became the first tennis player to surpass $50 million in career prize money. Williams also beat an American teenager in straight sets, eliminating Alexa Glatch of Newport Beach, Calif., 6-4, 6-1.

“Tricky match for me, playing a guy who’s got absolutely nothing to lose,” said Federer, seeking a sixth consecutive U.S. Open title.

No one has done that since Bill Tilden won the American Grand Slam tournament every year from 1920-25.

“That’s what I’m here for, trying to equal Bill Tilden’s record. But I’ve never met Bill Tilden. Never saw him play. So it’s hard to kind of relate to him in any way, except through records,” Federer said. “It’s fantastic to be sort of compared to someone who played such a long time ago, I guess.”

Other winners included John Isner, the 6-foot-9 American who knocked off No. 28-seeded Victor Hanescu of Romania in straight sets, including a 16-14 tiebreaker in the second; No. 21 James Blake; and French Open runner-up Robin Soderling.

Two-time major champion Amelie Mauresmo won easily, as did No. 7 Vera Zvonareva, No. 8 Victoria Azarenka, No. 10 Flavia Pennetta, No. 12 Agnieszka Radwanska and No. 14 Marion Bartoli, whose next opponent is Clijsters.

Bartoli, the 2007 Wimbledon runner-up, also just so happens to have been the first woman Clijsters played in her comeback. Clijsters beat her.

“I just have to go on court and think I’m still the player with the better ranking, so I’m supposed to win,” Bartoli said Monday. “This time I know what to do. I have a plan, so it’s going to be different.”

That was only one of several impressive wins for Clijsters already, including against Azarenka and French Open champion Svetlana Kuznetsova.

“Where I was the most surprised,” Clijsters said, “is how comfortable I felt out there from the beginning.”

She hit seven aces against Kutuzova, and won 60 of the 88 points. There also were some mistakes and some rust, including four double-faults.

But Clijsters knew that would be part of the deal as she decided to embark on a second tennis career. She started thinking about ending her retirement seriously early this year, after being invited to play in exhibition matches to test Wimbledon’s new Centre Court roof.

As Clijsters began to get in shape for that, she knew a return to the tour was what she wanted. Maybe even needed.

“I wasn’t surprised when Kim told me she wanted to give her tennis career another go. I knew she was young enough, and the more times she picked up the racket, the more the competitive bug bit her,” said her husband, Brian Lynch, an American who played professional basketball in Belgium. “I’m excited and happy for her — that our family has a chance to go on this adventure together.”

Clijsters looked at times Monday like she never went away: those deep forehands, all-over-the-court movement, the occasional volley.

“Just the match rhythm, I think, is something I have to get used to,” Clijsters said. “OK, matches like this today – I didn’t really get tested.”

Kutuzova explained why afterward: She was bitten by a spider a couple of days ago and had a bad allergic reaction, one that left parts of her arms red and swollen. A doctor gave her some medicine — too much medicine, Kutuzova said.

“I wasn’t even sure if I can play, because I was feeling very bad. When it was long points, I couldn’t breathe,” she said. “I couldn’t really see the ball, and everything was twisting.”

Still, Kutuzova was impressed by the woman across the net: Kim Clijsters, back on a Grand Slam stage, back at the U.S. Open.

“I didn’t see any difference,” Kutuzova said, “between how she was playing before and how she’s playing now.”