World number one Roger Federer returned to form after a bout of glandular fever with a 6-3 6-2 win over Guillermo Garcia-Lopez at the Pacific Life Open.
"I haven't played much, this is the difficulty," said Federer, who bounced back from two straight tour losses.
Sixth seed Andy Roddick was defeated by unseeded Tommy Haas 6-4 6-4 in Indian Wells in a tempestuous match.
Australian Open winner Maria Sharapova continued her unbeaten start to 2008, defeating Eleni Daniilidou 7-5 6-3.
Federer is searching for his first title of the year and is aiming to get back on track with a fourth crown in the California desert.
"Every first round you play at a big tournament is always a bit of pressure if you're number one seed," stated the 27-year-old.
"I could have taken more chances and won more easily but I'm happy with the way it went."
606: DEBATE
Roddick threw down his racquet and hit a ball out of the stadium as he went down to German Haas.
The pair were evenly matched, Haas had 30 winners to Roddick's 26 and both made 26 unforced errors, but Haas converted both his break chances.
"When I broke him, I really played some great points, backhand and forehand passing shots and forehand lobs, and that was really the only difference," conceded Haas.
Despite his on-court outbursts, Roddick was able to swallow his defeat after winning titles in San Jose and Dubai.
"It's a lot easier sitting here after this loss today having put together the body of work I have over the last month," he said.
"It's probably easier to take and probably affects your confidence a lot less."
Roddick was the biggest victim in the men's draw on Sunday, although number 12 seed Fernando Gonzalez was beaten 7-5 3-6 6-3 by Croatia's Mario Ancic.
There were no problems for Sharapova in the women's tournament as the fourth seed advanced with a straightforward win over Daniilidou.
"It was a very scratchy match from my side," commented the Russian. "I was just not seeing the ball, not moving that great.
"She's always tough because you never really know what to expect from her. So she doesn't give you a lot of rhythm."
Compatriot Svetlana Kuznetsova also went through to the fourth round following a battling 6-1 4-6 6-3 win over Slovakia's Dominika Cibulkova.
"I just stopped a little bit and lost my concentration," said the second seed, who recovered from a slump midway through the match.
"After being 5-0 down in the second set, I didn't want to go to the third set 6-0 down so I changed that to give me the key to play better in the third."
Defending champion Daniela Hantuchova beat China's Zheng Jie 6-4 6-2 and will now meet Sania Mirza, who saw off ninth seed Shahar Peer 6-7 (7-9) 7-5 6-3.
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