CARLISLE, PA — CARLISLE, Pa. -- Richie Petitbon, working on his 32nd year in the NFL as a player and a coach, has no trouble remembering how long he played before he suffered an injury that knocked him out of the lineup.
"Ten years and 11 games," said Petitbon, the assistant coach who runs the defense for the Washington Redskins.
"I tackled Bill Brown [of the Minnesota Vikings] out of bounds and landed on my elbow and ruptured my kidney," he said.
Petitbon knows the importance of staying healthy.
"You don't make many plays on the bench," he said.
Nobody understands that better than A.J. Johnson, the Redskins' fourth-year cornerback.
Johnson, who has been one of the outstanding performers in training camp, picked off two consecutive passes by Jeff Rutledge in practice Tuesday.
"He's a good athlete," Petitbon said. "He's a tough little guy, a good tackler, a good football player.
"Hopefully, this will be the year he'll stay healthy. He's not a malingerer. He's had some problems. Let's just hope he can hold it together. Here's a guy who can really be a good player, but you've got to play 16 games."
If Johnson can stay healthy, he's got the potential to be a starter. But that's a big if. Johnson has been hampered by injuries the past two years after making a fast start in his rookie season of 1989, when he started eight games despite an ailing right knee that got worse as the season wore on.
When the knee didn't respond to therapy after the season, Johnson underwent reconstructive surgery in June and was supposed to miss the entire 1990 season. He came back fast enough to play the final five games and was supposed to challenge Martin Mayhew for a starting position last year.
Johnson then broke his wrist in the first exhibition game against the Pittsburgh Steelers and didn't make it back until the sixth game of the year.
Johnson spent the rest of the season as a nickel back and then suffered another injury to the same knee in the first quarter of the SuperBowl.
He underwent arthroscopic surgery in the off-season, and he's ready again, but he knows he's got to prove he can stay healthy.
"Those injuries just happen," said Johnson, who went to Southwest Texas State and was drafted by the Redskins on the sixth round in 1989. "It's football. People get hurt. I can't worry about them.
"My main goal is to stay healthy."
Coach Joe Gibbs, who has little patience with players who get hurt, seconds the motion.
"If he can stay healthy, I think he'll play well," Gibbs said. "He's been very, very good."
Johnson is getting a lot of work in camp because he's playing left corner in place of Darrell Green, one of the Redskins' four holdouts. Johnson will start Saturday night in the exhibition opener against the Miami Dolphins.
Johnson, though, doesn't want it said he's replacing Green.
"I'm just there for the time being until he gets back," he said. "I have to do the same thing if he's here or not here. I have to try to have the best camp I can."
If Johnson stays healthy and continues to play well, he'll have a good shot at beating out Mayhew for the other starting spot when Green returns.
Johnson is considered a better coverage player than Mayhew, but Mayhew's edge is that he's only missed one game in the three seasons he's been with the team.
Now it's Johnson's turn to prove he can stay in the lineup.
"If you can play it [corner] well, you can last a long time," he said.
If Johnson survives Saturday night's exhibition opener against Miami injury-free, he'll already be ahead of last year's pace.
Incidentally, Miami said yesterday that quarterback Dan Marino, nursing achy knees, will not play Saturday night.
NOTES: The Redskins had their usual Wednesday night scrimmage at Carlisle High School last night. . . . Cary Conklin figures to start the first exhibition game at QB although Gibbs hasn't made it official yet. Jeff Rutledge is the backup and Stan Humphries is biding his time until Mark Rypien signs. He's then expected to be traded.