ST. LOUIS (AP) _ The St. Louis Rams' best-laid plans for a turnaround season are in the hands of a quarterback known only for his exploits in the Arena Football League and NFL Europe.

Kurt Warner, who has one quarter of NFL experience, became the starter by default when Trent Green suffered a season-ending knee injury in a 24-21 preseason victory over the San Diego Chargers on Saturday night.

Green tore the anterior cruciate ligament, sustained a third-degree strain of the medial collateral ligament in his left knee and also had cartilage damage.

Reconstructive surgery will be scheduled when the swelling subsides, in about 2-3 weeks. Dr. Robert Shively, the team physician, estimated the recovery period at 13 months.

The Rams acquired quarterback Paul Justin from the Oakland Raiders as insurance Sunday, giving up a seventh-round pick in next year's draft.

But for now it's ``Kurt Who?'' in the most visible spot as the Rams try to field a winning team for the first time this decade.

``I'm confident in my ability and the coaches are confident in my ability,'' Warner said. ``Now it's time to go out and prove to the rest of the world that I can be successful.''

Warner, 28, led NFL Europe in passing yards, attempts, completions and touchdowns in 1998 for the Amsterdam Admirals. Before that, he passed for 10,164 yards and 183 touchdowns in three seasons with the Iowa Barnstormers of the Arena Football League.

Last season, he beat out Will Furrer for the third-string job with the Rams. He was inactive the first 14 games and his only action came in the season finale, a 38-19 loss at San Francisco, in which he was 4-for-11 for 39 yards.

Now, suddenly, he's the man. He was in for only four plays in the second half Saturday night before coach Dick Vermeil, who had the second stringers in by that point, took him out to protect the new meal ticket. Rookie Joe Germaine, a fourth-round pick, went the rest of the way.

``He's paid his dues,'' Vermeil said.

Warner has huge shoes to fill even though Green, 29, has only one year experience as a starter. Green signed a four-year, $16.5 million free-agent deal with the Rams after a breakthrough season with the Washington Redskins.

Green threw for 3,441 yards and 23 touchdowns in 14 starts last year, and led Washington to a 6-3 finish. In the preseason, he was 28-of-32 for 406 yards with two touchdowns and one interception, and showed much better pocket presence than his predecessor, Tony Banks.

That all changed after Chargers strong safety Rodney Harrison, blitzing on the play, lunged at the back of Green's knees just after a pass was thrown. It wasn't a late hit, but Green's teammates felt it was unnecessary.

Offensive tackle Fred Miller, who went after Harrison and drew a personal foul, hoped the NFL would fine Harrison. Miller noted Harrison also took a couple of shots to the head of wide receiver Isaac Bruce, drawing an unnecessary roughness call on one of them.

``You could totally tell the guy was truly out to hurt somebody,'' Miller said. ``That's just the type of player he is and that we saw on film. He likes to come up and give a couple cheap shots.''

Harrison made the Pro Bowl last year, but he also has a reputation as a dirty player. He said, however, that if he had it to do over again he wouldn't have even blitzed.

``Sometimes the way I play is judged in a different light,'' Harrison said. ``I know in my heart that when I'm out there I try to play fair, try to play hard and do anything for my team to win.

``I don't try to do anything intentional. I'm sorry he's injured and everything, but I was just playing football.''

Green, who played with Harrison in San Diego in 1994, was critical of the play. But he didn't call for the league to fine or suspend him.

``I wasn't real happy with the way it turned out once I saw it,'' Green said. ``No matter what they decide, it's not going to make my knee heal any faster.''

For Green, it's time to move on.

``It's another hurdle, it's another obstacle,'' he said. ``I'm just going to work my tail off and get ready for next year.''

For Warner, it's time for a crash course.

``I'm willing to take anything anybody can give to me and I'm ready to learn,'' Warner said. ``I feel good with the skills I've got that I'm ready to keep fine-tuning every day, every minute, every hour.''