CINCINNATI - All Oliver Gibson could do was watch and wonder.

The Cincinnati Bengals' top defensive lineman of the last few years was relegated to rehabilitating a torn Achilles' tendon in the offseason. While he rebuilt his leg through therapy, new head coach Marvin Lewis rebuilt his defensive line through free agency.

Gibson knew his job wasn't safe.

''It's kind of tough when you're seeing new guys being brought in, and you're physically unable to do anything about it,'' he said. ''That was the worst part of it.''

Gibson, who got hurt Nov. 10, wasn't able to participate in the team's minicamps, where Lewis installed a new defense. When July rolled around, he was still learning and still limited by the leg injury.

Gibson played well enough in training camp to earn a role in the defensive line rotation. He was in for about 30 plays in the first two games, improving a little more each week.

He has made it through the worst part.

''He's made leaps and bounds since we opened training camp,'' defensive coordinator Leslie Frazier said. ''I believe as we get farther into the year, he'll become more like his old self. He's still not quite 100 percent yet. You can see that burst may not be quite there yet, but it's coming. It's better than it was two or three weeks ago.

''As he gets better stamina and stronger physically, he'll play more and more. We're counting on that.''

The Bengals weren't counting on anything after Gibson tore the tendon near the end of his eighth season in the NFL. Gibson, 31, was at a crossroads.

He was Pittsburgh's fourth-round pick in 1995, when Lewis was an assistant coach with the Steelers. Pittsburgh gave up on him after the 1998 season, and he came to Cincinnati as a free agent.

He was the only defensive lineman to start every game at the same position from 2000-01, leading the line in tackles in 2001. The torn tendon endangered his job.

''Marvin let me know, 'Hey, you're an older player, you've got a serious injury. If you don't come back, you're out of here,''' Gibson said. ''That's one thing about a coach that you can respect, the fact that he tells it straight up.''

Gibson, known for his durability, set about proving to Lewis that he could still play. He knew the coach wouldn't keep his spot open out of sentiment.

''I've earned everything that I've gotten,'' he said. ''I wouldn't be here if I didn't. I'm not a charity-case guy.''

He relished the season opener, which marked his official return from the injury. He's also looking forward to his game next Sunday against Pittsburgh, the team that still holds a special place in his heart. Gibson is friends with running back Jerome Bettis and a few other Steelers.

''It's just a big game to me during the week,'' Gibson said. ''Then the minute I go out there and see that black and gold and see my old coaches and a couple of my old teammates and Jerome starts with the playful ribbing - 'You can't catch me, OG' - that's when it becomes very personal and very playgroundish."