ATLANTA -- After withdrawing from the Atlanta Open, Mardy Fish was just thankful he wasn't hurt more seriously.
Fish stumbled to his left while trying to return a drop shot in the second set and his left ankle appeared to buckle as he got near the steel net post.
"I did everything I could just to bring my head back," he said. "That brought my right leg out, sort of sliding and jarring it back and (turned) the inside of the right ankle. It was going to be either my knee, my ankle or my head. Thankfully it was my ankle."
Fish, the No. 2 seed, was leading Gilles Muller of Luxembourg 6-4, 3-2 in the second round when he pulled out of the match. He said the injury had not yet been diagnosed and planned to have an MRI either Thursday night or today.
After dropping his racquet and falling to the hard-court surface, Fish stayed on his back for about a minute before limping to the sideline for a short break. Fish returned to finish the fifth game of the second set with two aces. After he and Muller changed sides, Fish waved his opponent off.
"There was some sharp pain when I was walking after getting up from the chair for the changeover," he said. "I knew it was a little bit worse than I thought initially."
Muller will play Matthew Ebden, a 6-7 (6), 6-4, 6-4 winner over James Blake, in the quarterfinals.
This year has been tough on Fish, the world's No. 13-ranked player.
He underwent a heart procedure on May 23 to correct an arrhythmia and played in just one event, a fourth-round loss at Wimbledon to France's Jo-Wilfried Tsonga, from early April in Houston until Thursday.
Fish received a first-round bye in Atlanta and was playing his first match on the new courts at Atlantic Station.
"This is a comfortable place for me, so naturally I enjoy playing here," he said. "It's a bummer. What can you do? I've been in this position before. It happens."