Published: May 31, 2012 1:10 PM EDT
Updated: Jun 01, 2012 6:31 AM EDT

PARIS (AP) - Grimacing in pain with almost every step, Andy Murray nearly had to call it quits Thursday because of a bad back at the French Open.

Instead, the fourth-seeded Brit rebounded from an awful first set to beat Jarkko Nieminen 1-6, 6-4, 6-1, 6-2 and reach the third round.

Murray could barely walk straight when the match started on Court Philippe Chatrier, gingerly trotting around the red clay with the equivalent of a big target on his back. Nieminen took advantage, at the beginning.

But after losing the first four games, Murray called for a trainer. He then broke back to 4-1, and needed more treatment during the changeover.

The first set was over quickly, and Murray took yet another break for treatment. That one really seemed to do the trick.

Despite being broken to open the second set, Murray started to move better and make his shots count. By the time he broke back to even the score at 4-4, Murray was the one getting stronger.

Last year, Murray injured his right ankle at the French Open, but he still made the semifinals. This year, he skipped the Madrid Open with a back problem and said it was still affecting him after a three-set loss to Richard Gasquet in the third round of the Italian Open.

It clearly bothered him Thursday, but he still managed to come through.

Wimbledon champion Petra Kvitova also reached the third round, beating Urszula Radwanska of Poland 6-1, 6-3.

The fourth-seeded Czech was never really tested on Court Suzanne Lenglen, saving all three break points she faced.

Kvitova secured her first Grand Slam title at Wimbledon last year, and then won the WTA Championships. Although she has yet to win a title in 2012, she is seeded fourth in Paris and is expected to go deep into the tournament.

"I don't have any expectation. I know that last season was great for me, and it will be very tough to have similar result as last year," Kvitova said. "So I know this season will be very tough with the pressure and with everything else."

Radwanska is the younger sister of third-seeded Agnieszka Radwanska, who reached the third round on Wednesday by beating seven-time Grand Slam champion Venus Williams.

Later Thursday, second-seeded Maria Sharapova was to face Ayumi Morita of Japan, and defending champion Li Na was to play Stephanie Foretz Gacon of France. Also, defending men's champion Rafael Nadal was scheduled to be action against Denis Istomin of Uzbekistan. Nadal is looking for a record-breaking seventh title at Roland Garros.

For Roger Federer, setting records on the tennis court is becoming ho-hum.

The perks that come with them, like dining with Queen Elizabeth II, are the things to really remember.

"Yes, I have had lunch next to the queen - with the queen, basically," Federer said. "Big honor, obviously ... Thank God, she came."

Federer beat Adrian Ungur of Romania 6-3, 6-2, 6-7 (6), 6-3 Wednesday in the second round. With the win, the 16-time Grand Slam champion broke a record he shared with Jimmy Connors for most career victories at major tournaments in the Open era, which began in 1968. He is now 234-35 in tennis' top four tournaments, an .870 winning percentage.

But he was less than his dominant self, wasting two match points in the third set before losing the tiebreaker.

"Instead of being aggressive, I let him show me what he could do," Federer said. "He played two beautiful shots, and then I started not playing very well."

Novak Djokovic also advanced to the third round, as did top-seeded Victoria Azarenka of Belarus.