| By New York Tennis Magazine Staff
Photo credit: Kenneth B. Goldberg

Spain's Rafael Nadal defeated American Mardy Fish 6-2, 3-6, 7-6 (3) at the ATP World Tour Finals on Sunday at The O2 Arena in London, England in a three-hour-plus marathon match. Nadal overcame a stomach ailment to defeat Fish in opening round action in Group B.

"I felt very bad from the stomach since the beginning of the third [set]," Nadal said. "I was seriously really lucky for the victory, and I for sure am very happy."

Also in Group B action, Switzerland's Roger Federer defeated France's Jo-Wilfried Tsonga on Sunday in opening round action, 6-2, 2-6, 6-4. Federer's win advances him to play Nadal as the two will face each other for the 26th time. So far in 2011, Federer has been on the losing end of all three meetings with Nadal. 

"It's not always in your control when you play Jo," Federer said. "That's the beauty of it. I kind of enjoy that to some degree. But I think also partially because it was a first-round match, I think that's maybe why we saw some ups and downs from both players."

In Group A action, it was Spain's David Ferrer with a 6-4, 7-5 straight-sets upset stunner over hometown favorite, Great Britain's Andy Murray. Murray was experiencing issues with his groin which may force him out of the event. 

"Yeah, I mean, I had a problem with my groin. I have to see how it goes for tomorrow," said Murray. "I'll decide tomorrow whether or not I keep playing. If it wasn't slams or this event, I wouldn't have played."

Ferrer will play the winner of the final Group A opening round match between world number one-ranked Serbian Novak Djokovic and Tomas Berdych of the Czech Republic. Murray, depending on whether or not he decides to withdraw from the event over the groin issue, will face the loser of the Djokovic-Berdych match.