MELBOURNE, Australia -- Roger Federer kept his cool on a scorching hot second day at the Australian Open, starting his record 57th consecutive Grand Slam tournament with a straight-sets victory in his first competitive match in front of new coach Stefan Edberg.
Top-seeded Rafael Nadal advanced to the second round when opponent Bernard Tomic, bothered from the start by a left leg injury, retired from their match after losing the first set 6-4. Some in the capacity crowd of 15,000 at Rod Laver Arena booed lustily when Tomic indicated he could not continue.
Federer played the second match at Rod Laver Arena on Tuesday, and the temperature topped 106 degrees during his 6-4, 6-4, 6-2 win over Australian wild-card entry James Duckworth. He kept the points as short as possible and gave No. 133-ranked Duckworth only one look at a break point in the 1-hour, 46-minute match.
Asked how he handled the heat, the 32-year-old Federer said: "I'm here. I'm speaking. Actually, it's not crazy. I'm feeling OK right now."
"It was very dry, just hot, stinging sort of sun," he added later. "Depending on where you come from, it has a bigger effect on you, this type of heat. So it's very personal, and it can become just a very mental thing -- you just can't accept that it's hot."
Federer now owns the record for playing the most consecutive Grand Slam events, another milestone in a career that has already resulted in 17 major titles for the Swiss star. He said it was "great fun" to finally play in front of childhood hero Edberg, whom he hired on a part-time basis last month.
"I used to watch his matches and get inspired," Federer said, then added: "He warmed me up. ... I won!"
Nadal said he felt for Tomic, who called a medical timeout after three games and twice more before he quit.
"I know how tough is this situation, I had the same a few years ago at this tournament,'' he said. "Since the beginning, I saw a little bit he had some problems on the leg.''
He did not face a break point on his serve and took advantage of six of his 13 break-point opportunities.
No. 4-ranked Murray has played only two official matches since minor back surgery in September and said he needs to work his way into the tournament. He has reached three Australian Open finals but has yet to win the season's first major. Since hiring Ivan Lendl as coach, though, he has made his Grand Slam breakthroughs with titles at the US Open in 2012 and Wimbledon in 2013, ending droughts stretching to the 1930s for British men at the majors.
"I'm obviously more confident than I was a few years ago but I'm just lacking match practice," Murray said. "I'm desperate to try and win here. I've had a lot of near misses, I've played some of the best tennis of my career here, but it hasn't been good enough yet."
Del Potro, the 2009 US Open champion, made several unforced errors in dropping the first-set tiebreaker but cleaned up his game in the second set and controlled the rest of the three-hour match.
The Argentine player is coming off a victory at the Sydney International tournament last week, his 18th career title. He hadn't lost to a player ranked as low as No. 130-ranked Williams since Tokyo in 2009, when he fell to No. 189 Edouard Roger-Vasselin.
Former No. 1-ranked Hewitt, who beat Federer in last week's Brisbane International final, had a match point late in the 4-hour, 18-minute match. But he was broken in that 11th game before Seppi held serve in the next to close out the 63-minute fifth set.
The closest Hewitt has come to capturing the title at his home Grand Slam event was as losing finalist to Marat Safin in 2005.
No. 10 Jo-Wilfried Tsonga, a 2008 Australian Open finalist, advanced along with No. 11 Milos Raonic, No. 22 Grigor Dimitrov and No. 31 Fernando Verdasco. No. 16 Kei Nishikori beat Australian Marinko Matosevic in five sets.
Temperatures hit 108 degrees on the second day of the tournament, with the forecast predicting more heat until Friday. A hot, gusty breeze swirled across the venue all day, making conditions more challenging instead of cooler.
Some players struggled. Canadian qualifier Frank Dancevic said he blacked out during a 7-6 (12), 6-4, 6-3 loss to No. 27 Benoit Paire of France. Dancevic had treatment in the second set but continued. On the women's side, Peng Shuai got sick on court but also continued her match.
"I think it's definitely hazardous to be out there," Dancevic said. "It's dangerous."
Tim Wood, the chief medical officer at the Australian Open, conceded players experienced "heat-related illness or discomfort," but added: "None required significant medical intervention after they had completed their match."
Tournament director Craig Tiley endorsed those sentiments. A ball girl was treated for heat stress during a morning match, and the tournament shortened rotations for the ball kids to 45-minute shifts and added extra precautions.
Players draped bags of ice over their necks and shoulders and sat under cover during the changeovers across Melbourne Park. They retreated into the shade at the back of the courts between points. A ball kid was treated for heat stress during a morning match. Meanwhile, spectators on outside courts covered their heads and shoulders with damp towels to cool off and queued up to stand in front of large electric fans blasting water at their faces.
"It looks terrible for the whole sport when people are collapsing, ball kids are collapsing, people in the stands are collapsing," the Wimbledon champion said.
The crowd for the day session was 35,571, down almost 12,000 from Day 1.
As well as the heat, there were injuries and retirements. No. 13 John Isner, the only seeded American man in the draw, retired after losing the first two sets 6-2, 7-6 (6) against Martin Klizan. He called for the trainer after the tiebreaker, tapped his racket on the ground three times while deliberating whether to go back out and played for only a few minutes in the third set.
Isner attributed it to the same right ankle problem that bothered him last week on the way to the title in Auckland, New Zealand.
Philipp Kohlschreiber of Germany didn't make it onto the court, withdrawing before his first-round match due to a strained left hamstring.
The Associated Press contributed to this report.