Defending champion Rafael Nadal survived a serious scare against Radek Stepanek before recovering to reach the third round of the BNP Paribas Open in Indian Wells.
Stepanek, an experienced and tricky customer, came out firing and dominated the first set.
Nadal rallied to level but found himself 0-40 down in the sixth game of the decider before eventually pulling out a 2-6 6-3 7-5 victory.
The Spaniard, who next meets another quirky player in Alexandr Dolgopolov, revealed the back injury that severely hampered him in the Australian Open final is still on his mind.
Nadal served eight double faults, and he said: "I was a little bit scared for the back. I am not feeling yet 100 per cent confident with my serve.
"He is not the right player to play against in the first match because what you want to find is rhythm and against him every point is different."
Roger Federer extended his winning run with a 6-2 7-6 (7/5) victory over Paul-Henri Mathieu.
The Swiss came into the tournament as the form player on the men's side after winning the high-profile tournament in Dubai last week.
Federer's countryman Stanislas Wawrinka looked to have a difficult outing against 6ft 10in Ivo Karlovic for his first regular tour match since beating Nadal to win the Australian Open in January.
But the third seed avoided any drama in a 6-3 7-5 win.
He said: "I'm just feeling great and happy to be back, especially here. It's an amazing tournament.
"I was a little bit scared about the way I was going to play. But after five or six days on the practice court with (coach) Magnus (Norman), I was feeling really good. I'm really happy with my level. I really think I'm playing great tennis."
Lleyton Hewitt will have to wait a little longer for his 600th win after losing 7-6 (7/5) 6-4 to in-form 17th seed Kevin Anderson while Jerzy Janowicz's struggles continued.
The 6ft 8in Pole looked the coming man when he reached the Wimbledon semi-finals last summer and gave Andy Murray a fright, but he has reached the last four just once in all his tournaments since.
Janowicz served for the match and held match point against Colombian Alejandro Falla in Indian Wells but lost out in a deciding tie-break.
It was another bad day, meanwhile, for the US men, with Ryan Harrison, Sam Querrey, Tim Smyczek and Michael Russell all losing.
That left John Isner, who has yet to play his first match, as the only home player left in the men's singles.
Harrison's defeat came against Italian Fabio Fognini, who had an extraordinary rant at umpire Lars Graff over a line call in the second set.
Tenth seed Milos Raonic returned to action after ankle problems with a tight three-set win over Edouard Roger-Vasselin while there were also victories for Tommy Haas, Kei Nishikori and Gael Monfils.
In the women's event, top seed Li Na recovered from 4-2 down in the second set to defeat Chinese compatriot Zheng Jie 6-1 7-5.
Li is the leading player for the first time at a WTA Premier Mandatory tournament, and she said: "At least I'm still in the tournament.
"If I see the result of course I'm happy, but I still feel I have so many things I can improve."
Maria Sharapova has turned her focus back to tennis after carrying the Olympic torch into the stadium at the Winter Olympics in Sochi last month.
And there was no sign that the Russian has been distracted from her day job as she eased past German Julia Goerges 6-1 6-4.
Another of the top-five seeds was sent packing as Angelique Kerber followed Victoria Azarenka out of the door with a 2-6 7-6 (7/5) 6-4 loss to Maria-Teresa Flor.
It was a bad day for the Germans, with Wimbledon runner-up Sabine Lisicki also losing.
Eighth seed Petra Kvitova celebrated her 24th birthday with a 6-1 6-3 win over American wild card Coco Vandeweghe while Australian Open runner-up Dominika Cibulkova beat Donna Vekic 6-3 6-2.
Ana Ivanovic survived a two-and-a-half-hour battle with Elina Svitolina, winning on a deciding tie-break.