No Longer Covered by Warranty : Chargers: An injury last year reminded Dennis McKnight he was not invincible. This year, he’s fighting to regain his position on the offensive line.

Dennis McKnight had begun to think he was indestructible.

For seven seasons, the Chargers put him at center, guard or tackle, and he hammered away at the guy on the other side of the line. He wasn’t a bury-you-to-the-turf type, but he was steady and persistent. Few people reached the quarterback by going past McKnight.

Throughout his seventh season in 1988, opponents kept coming up to him after the game and saying: “Man, you’re a hell of a player. I’m going to vote for you (for the Pro Bowl).” It was nice to hear, particularly for a guy who played much of the season with a knee so stiff he that couldn’t make it to the coin toss.

McKnight wound up as a Pro Bowl alternate that year, and several players told him he should have been the starter.

Entering the 1989 preseason, he had started 77 consecutive games. The thought never entered his mind that he would do anything but play 16 or 17 seasons. And it surely wouldn’t be him who was knocked out of a game with an injury--it would be the other guy, the one who didn’t train as hard as he did.

But one play changed his thinking, his career and his life. In the final exhibition against Phoenix last season, he suffered a torn quadriceps tendon and was sidelined for the rest of the year.

Now, as he slowly begins to rediscover the form that drew attention in 1988, thoughts of invincibility are long gone. He is aware that anything is possible. He could be demoted to backup. This could be his last season. Who knows? There is always that possibility that he will be released.

“You never know,” he says. “I know I’m still a good player, but if I don’t fit into schemes or future plans, then hey, things can happen.”

McKnight is the only player remaining on this team to have worn a Charger uniform in the NFL playoffs. He can tell by looking around him that he isn’t one of the kids anymore. The other faces are younger, the legs a bit more spry.

“I do feel older,” he says. “It is a sign that the end is coming. I’m appreciating and enjoying things more now. I won’t hate practice as much. I think when the season starts, I’ll enjoy it more.”

And that’s because he came awfully close to seeing his football career slip through his fingers. The night he was hurt, he overheard the doctor whisper: “Boy, it’s too bad Conan’s done.”

Conan is the nickname McKnight was given by teammates for his dedication in the weight room. Fittingly, long hours of lifting brought him back to the field this year.

Certainly, there was a lot more to deal with than physical training. The hours he didn’t spend rehabilitating his leg went by slowly. All sorts of thoughts came to mind. Could he come back? If not, what then? How would he support his family? Should he go look for a coaching job?

“You don’t sleep at night, so millions of things run through your head,” he says. “All of a sudden it’s like ‘Wow, I’m human.’ ”

Then there were the reminders of what he was missing. One time, he went to the stadium to wish the team luck before it took off for Los Angeles to play the Raiders. Everything was fine until the bus pulled away, and then it hit him. He wasn’t going. And he says that tore him apart.

His two closest friends on the team, Don Macek, who retired at the end of last season, and tackle Joel Patten would come by his house after each game and take him out on the town. Football was never discussed.

“The biggest thing he needed was not to talk about football,” Patten said. “He needed to be one of the guys again.”

This year, he isn’t really one of the guys anymore, and he knows it. In some ways, he can’t afford to be. The younger players stay up at night to watch television or play games. A veteran such as McKnight, who has had four knee operations and will be 31 in September, needs to store up his stamina for two-a-day workouts.

“I just don’t have the energy to stay up,” he says. “I need to go to bed, and I need to rest.”

The first few days of camp this season weren’t kind to McKnight, who worried constantly that he wouldn’t pick up the new blocking schemes and that he was headed for a quick trip to the cut list. His wife, Jodi, and Patten kept telling him it was only the first week and that he should be patient.

“All I did,” Patten says with a laugh, “was take the gun away.”

Gradually, things began to fall into place. All the off-season training has made him stronger physically, and he is getting a grip mentally.

“That first week I was depressed,” McKnight says. “But now it’s like that didn’t even exist. I have my old confidence back.”

Alex Gibbs, Charger offensive line coach, says it’s usually the guys with more years under their belts that are most protective of their territory.

“That’s the paranoia that goes with the position,” Gibbs says. “The longer they’re in, the more it gets that way. They’re afraid of being cut, afraid their career is over.”

The biggest threat to McKnight’s career is Larry Williams, a Plan B free agent acquired in March, 1989, who spent last season on the reserve-physically unable to perform list. Williams, 27, may push McKnight for the starting guard position by the beginning of the regular season.

“It’s Dennis’ job at this point,” Gibbs said. “Larry can’t just play as good as Dennis, Larry’s got to play better than Dennis.”

McKnight concedes he is still rusty after a year without football. But when he takes a look around, he figures he stacks up well next to his competition.

“I might not be the best lineman of all the guys we’ve got in camp, but I think I’m the steadiest,” he says. “I see myself coming back to the form I once was, which is not a great dominating lineman, but I was very steady. You could throw me in there and say ‘I know this guy’s going to do this, and we can leave him alone.’ ”