The ankle injury that Bernie Kosar thought was only a sprain turned out to be a fracture that will force him to miss at least six weeks.

X-rays taken at the Cleveland Clinic on Tuesday revealed a hairline fracture in Kosar's right ankle, injured in the first half of the Cleveland Browns' 27-23 Monday night loss to the Miami Dolphins.Kosar played the entire game, limping throughout the second half but still managing to throw two fourth-quarter touchdown passes that gave the Browns a short-lived 23-20 lead. Miami won it on Mark Higgs' 1-yard run with seven seconds left.

"It happened either in the first or second quarter," said Kosar, who was sacked twice and hit hard several other times in the first half. "I tried not to think about it. I tried to move around a lot on the sidelines to keep it loose, and just tried not to think about it."

It's not the first time Kosar has stayed in a game after breaking a bone. He fractured his right thumb in the second quarter against Atlanta in December 1990 but played the rest of the game.

"He is one hell of a competitor, and obviously this is a big blow to this team," coach Bill Belichick said.

Browns owner Art Modell called Kosar's play "the most extraordinary display of courage I've ever seen in football." Modell compared it to former Rams defensive end Jack Youngblood's playing with a broken leg in a 1979 playoff game against Dallas.

"When you think about the way he moved, the way he exposed himself to further injury and the way he played in the fourth quarter last night, you can have nothing but respect for this special young man," Modell said.

The Browns' backup quarterback is Todd Philcox, who completed 20 of 49 passes for 317 yards with two touchdowns and two interceptions during the preseason. He didn't play in either of the first two regular-season games, and appeared only briefly in four games for the Browns last year.

Kosar, 28, became the Browns' starter during his rookie season, 1985, after leading the University of Miami to a national championship in 1983. He surpassed 20,000 career yards two weeks ago in the Browns' season-opening loss to the Indianapolis Colts.

Monday night, he completed 19 of 28 passes for 230 yards, including 11 of 15 for 172 yards in the second half.

"I thought Bernie's performance in the second half last night was outstanding before I knew about his injury," Belichick said. "When you put the way he played and the way he took charge in the context of the injury, it shows you what a special performance it was."