The 11th-seeded Agassi was looking vulnerable in the first set. He was helpless as Fish, a finalist here last year, saved four break-points with booming serves. Agassi dropped his own serve in the ninth when he netted a forehand.

Fish continued to command the match until the second-set tiebreaker, but the back injury which kept him from playing in Toronto last week became too painful to ignore in the third set.

"It was disappointing the way a match like that ends, but I was happy with the fact that the way I was playing as the match went on was getting better," said Agassi, 34.

Fish said his main concern at the end was not to make his injury worse.

"My goal out there was not to injure it more - to try to win, but not to injure it more," said Fish, who lost to fellow American Andy Roddick in a marathon final here last year.

Agassi, who numbers two trophies from Cincinnati amongst his 58 career titles, again faced the almost inevitable questions about his retirement plans.

But even though he hasn't won a title since Houston in May 2003, Agassi clearly still has the urge to compete.

"I'm pushing myself to get back to what I believe I can still do as far as how I feel out there," Agassi said.

Former world No. 1 Lleyton Hewitt of Australia, who won titles at Sydney and Rotterdam earlier in the year, had little trouble dispatching Alex Bogomolov of the United States 6-2, 6-4.