There was an anxious moment for fans — and perhaps most of all tournament organizers — Tuesday night when top-seeded Mardy Fish crumpled on his sore right ankle in the first round of the Citi Open.

Two weeks ago in Atlanta, when Fish originally was hurt, he had to retire while leading in the second set. What would Fish do now as he trailed unseeded German Bjorn Phau in the first set?

A doctor was summoned, but Fish quickly returned only to lose the final point of the first set. After limping around the court early in the second set and facing a service break, Fish hit back to back aces, his ankle loosened up, and everything changed in a 4-6, 6-1, 6-2 victory.

“You’d be surprised at how much better it feels when you’re up a break as opposed to down a break,” said Fish who finished with 15 aces. “It was nice to get the momentum a little bit in the second set.”

Fish will get an extra day to rest his ankle before playing Thursday in the round of 16 against wild card Ricardas Berankis of Lithuania.

“The ankle is probably 75 percent, but not hampering me in a bad way,” Fish said. “It doesn’t feel great, but it doesn’t affect my movement.”

Fish was the only one of the top four seeds who faced a significant challenge on Tuesday. No. 2 Alexandr Dolgopolov of the Ukraine, No. 3 Kevin Anderson of South Africa, and No. 4 Tommy Haas of Germany all won in two sets, with none of the losers winning more than four games.

Wednesday on the stadium court, Haas will play Leonardo Mayer of Argentina at approximately 5:30, followed by unseeded James Blake against qualifier Marco Chiudinelli of Switzerland. In the nightcap, Dolgopolov takes on Ruben Ramirez Hidalgo.

On Tuesday night, the Citi Open appeared in danger of losing its top seeded male as Fish was floundering and Phau appeared full of confidence, especially when Fish went down late in the first set.

“I sort of dove for a ball and probably shouldn’t have,” Fish said. “Probably thought I was on the grass and I wasn’t.”

But the roles reversed early in the second set as Fish won seven straight games, including three service breaks in which Phau didn’t win any more than three points.

With a watered-down field this week due to the Olympics, Fish said the Citi Open is “absolutely an opportunity,” as he looks to regain his form after undergoing a procedure this spring to correct a heart arrhythmia. Fish, who is ranked No. 15, hasn’t won since July of last year. He believes his physical problems are over, but that he still has mental hurdles to clear.

“When I don’t feel 100 percent, my mind can go in bad places,” Fish, 30, said. “That’s the hardest part for me right now.”

Unlike other players – men and women – at the Citi Open who have expressed disappointment at not making it to the Olympics, Fish is here by choice. He won a silver medal at the 2004 games in Athens, then decided to stick with the ATP Tour as it prepares him best for the U.S. Open and Davis Cup.

“I had an unbelievable experience in Athens. A lot of it has to do with scheduling,” Fish said. “Going back and forth [to Europe] is very tough. I travelled too much in the beginning of the year. … Less travelling, staying closer to home, staying in cities where I’m comfortable, after all this happened with my heart, it’s a way better decision for me.”