Milos Raonic advanced to the second round of the U.S. Open, but fellow Canadian Vasek Pospisil missed a chance to join him after what he called a "clear mistake from the umpire."

The 10th-seeded Raonic from Thornhill, Ont., had a lot less drama in his opener as he defeated Italian qualifier Thomas Fabbiano 6-3, 7-6 (6), 6-3.

"I know he's very capable, I remember him from juniors," Raonic said of Fabbiano. "He got through quallies, so he must be playing well in that situation. I just sort of dealt with it as best I could, and I'm happy with how the result turned out."

Raonic will face Pablo Andujar in the second round after the Spaniard beat Thiemo de Bakker of the Netherlands 6-4, 6-4, 6-4.

Raonic put on a serving display against the 179th-ranked Fabbiano, who was making his Grand Slam debut. The Italian gave Raonic only the slightest hint of trouble when he got a break back in the second set for 4-all before losing the set in a tiebreaker.

Raonic took a 4-2 lead in the third set and sealed the victory with a series of untouchable serves. He finished with 52 winners, including 28 aces.

"Serve helped for sure, got me get through a lot of difficult situations," Raonic said. "I was struggling definitely from the baseline, but when I sort of needed it I was able to pick it up on both sides.

"In general, it was a good day."

Raonic sees some parallels between his next opponent Andujar and himself.

"He started doing well in 2011, just like me. He's very consistent. He can be aggressive, especially with his forehand, and I've got to play more aggressive than I did today," he said.

"I've got to clean up a bit off the baseline and hopefully serve like I did today."

Tough loss for Pospisil

Pospisil was left fuming Tuesday after a tough 4-6, 3-6, 7-6 (9), 6-2, 7-6 (10) loss to Brazilian qualifier Rogerio Dutra.

With the fifth-set tiebreaker tied 10-10, the umpire overruled a linesperson's call on Dutra's shot that was initially ruled long. That gave Dutra match point, which he then converted to complete the win over the native of Vernon, B.C.

"It was a clear mistake, a huge mistake," Pospisil said. "That ball was 2-3 inches long. There was no doubt — the next thing he called it in. Something has to be done about mistakes like that.

"To overrule on the baseline is absolutely terrible. The linesperson called it out, it was not even close. I was in a state of shock and anger. I've never experienced a call like that, especially at this stage of a grand slam match.

"It doesn't excuse that I didn't convert leading to that point, but I would have had another match point and maybe I would have gotten it."

The match was played on Court 14 where replay challenges are not available. It was completed after being delayed by rain Monday night with Pospisil up two sets to one, but trailing the fourth set 4-0.

"In the third set I had stopped serving well, I had nothing in my legs and I could feel my body going downhill," he said. "I had cramps but I felt better today."

Novak Djokovic cruises to win

Top-seeded Novak Djokovic saved seven of eight break points Tuesday night to start the U.S. Open with a 6-1, 6-2, 6-2 victory over former junior world No. 1, Ricardas Berankis of Lithuania.

The victory took only 82 minutes for Djokovic, seeking his second title and fourth straight final at Flushing Meadows.

It was a quiet evening at Arthur Ashe Stadium, where the packed crowd barely cheered during the most routine of matches.

One of the few exciting moments came on the first point of the third set, when Djokovic lobbed Berankis and Berankis replied with a backward shot between his legs that Djokovic calmly flicked away for a volley winner.

The top-seeded Serb hit 28 winners, with only nine unforced errors.

Federer moves on

At this point in his career, Roger Federer recognizes the importance of a little extra work.

That's why the owner of a record 17 Grand Slam titles, and the man who spent more weeks ranked No. 1 than any other, was out there on a U.S. Open practice court late Tuesday afternoon, putting in some training time shortly after finishing off a 6-3, 6-2, 7-5 victory over 62nd-ranked Grega Zemlja of Slovenia in the first round.

At 32, at his lowest ranking, No. 7, in more than a decade, coming off a stunningly early exit at the previous major tournament — one of a series of newsworthy losses lately — Federer is OK with making some concessions. He insists his passion for tennis is still there.

"I'm in a good spot right now," Federer said. "I want to enjoy it as long as it lasts."

He made it sound, though, as if it isn't as easy to enjoy things the way his results have been going.

Federer entered Tuesday 32-11, a .744 winning percentage that doesn't sound too bad, until you consider his career mark at the start of this season was .816, and he's had years where he went 81-4 (.953). and 92-5 (.948). He's only won one tournament in 2013, which would be great for some guys, but Federer topped 10 titles three times, and hasn't won fewer than three in any season since 2001.

"Clearly, when you win everything, it's fun. That doesn't necessarily mean you love the game more. You just like winning, being on the front page, lifting trophies, doing comfortable press conferences. It's nice. But that doesn't mean you really, actually love it, love it," said Federer, whose streak of 36 consecutive Grand Slam quarterfinals ended with a second-round defeat at Wimbledon against an opponent ranked 116th. "That maybe shines through maybe more in times when you don't play that well. For me, I knew it — winning or losing, practice court or match court — that I love it."

As Federer took the first step toward a possible quarterfinal meeting with nemesis Rafael Nadal, No. 5 Tomas Berdych and No. 10 Raonic also picked up straight-set victories.

On a day that American men went 5-1, led by No. 13 John Isner and No. 26 Sam Querrey, a handful of seeded men made quick departures. No. 14 Jerzy Janowicz of Poland, a semifinalist at Wimbledon last month, was the most surprising to go, although he was treated by a trainer for a painful back during a 6-4, 6-4, 6-2 loss to 247th-ranked qualifier Maximo Gonzalez of Argentina.

"It was like someone puts a knife through your lower back," Janowicz said.

Volatile character

Janowicz is a volatile character, and that was on full display Tuesday. He pounded two balls in anger into the stands. He swatted one serve underhand. He chucked his racket. He argued with the chair umpire.

Joining him on the way out were No. 15 Nicolas Almagro, No. 25 Grigor Dimitrov and No. 28 Juan Monaco.

Federer says he doesn't fret about being seeded seventh at Flushing Meadows, a year after being seeded No. 1. Not since 2002, when he was 13th, had Federer been so low at the U.S. Open.

That didn't really affect Tuesday's opponent in Arthur Ashe Stadium. All that mattered to Zemlja, who owns fewer Grand Slam match wins, eight, than Federer owns Grand Slam titles, was that he was facing what he considered an impossible task.

"If he's the seventh seed or fourth seed or first seed, for me, that's totally irrelevant," Zemlja said. "He achieved so much. He's the best player of all time. So I don't think people can actually say something [negative] about the way he's playing. You're losing matches, you're winning matches — that's just tennis, and I'm sure he's going to perform better than maybe he has done in the last few tournaments."

Difficult as things have been for Federer, he certainly remains capable of summoning his best strokes. A bad lower back has bothered him this season, and he's experimented with a larger racket head, but with his old equipment in hand Tuesday, a healthy-looking Federer collected 35 winners and only 16 unforced errors.

Wearing neon-pink-and-grey shoes with a "5" etched inside a silhouette of the U.S. Open trophy on the right heel — the number of titles he's won in New York from 2004-08 — Federer won 20 of the 21 points he played at the net and 62 of the 80 points he served. To cap the first set, Federer spun a 95 mph ace into a corner. To cap the second, he hit a 118 mph service winner that forced Zemlja into a backhand return so wild that it sailed directly into a guest box in the stands, where Federer's agent happened to catch the ball on the fly. And to cap the third, Federer pressed forward for a swinging forehand volley winner.

"I decided ... to play aggressive," Federer summed up. "I was happy the way I played, you know, overall. I mean, it's a first round, after all."

With files from The Associated Press