AUBURN – Tez Doolittle spent three-plus seasons as a backup, lost two more to injury and now is an overnight success.

The Auburn defensive tackle is going to make his first career start Saturday against Tennessee for the 15th-ranked Tigers, making the most of an NCAA-granted sixth year of eligibility.

Doolittle claimed the starting job after playing what coach Tommy Tuberville described as the best game of his career against No. 5 LSU.

“It means a lot to me,” Doolittle said. “I’ve been working my tail off trying to get to that spot, and I finally got there now. I’m really excited about it. I’m just hoping I can hold it down.”

Just making it this far is a pretty big accomplishment. Doolittle missed last season with a torn Achilles’ tendon, the most serious setback in an injury history that includes two shoulder operations and a dislocated kneecap.

Now, the 23-year-old who could have gone down as an underachiever is the Tigers’ feel-good story. He had four tackles and was in on a sack against LSU, and his nine stops already matches his best season.

Doolittle was soaking in the big-game atmosphere after a season out of football.

“That crowd Saturday, you couldn’t hear anything,” he said. “Everything’s going through your head. I was like, ‘I can’t believe I’m out here doing this again.’ I was just like a little kid all over again.”

And now he’s set to make his first start. Finally.

Doolittle said he didn’t feel like he was playing well against LSU. When the coaches sent him to work with the starters in Sunday’s practice, he said, “I was thinking it was just because those were the mistakes I messed up on or whatever.”

Fellow defensive tackle Sen’Derrick Marks said the elder statesman of the defense brings energy to the field.

“Every time he makes a tackle, he’s got that emotion,” Marks said. “Then every time we get off the field, he’s like, man, I can’t believe this really happened to me after all I’ve been through.

“Having that chance to get back to play and once he gets that chance play at a level that he never played at — it means a lot to him, it means a lot to me, it means a lot to a lot of guys on the team.”

Doolittle said he returned for his sixth season just hoping to play a role spelling the starters at times. Anything to get back on the field. He said doctors had predicted 16 months of rehabilation after his injury in August 2007, a timetable that would have ended his college career.

His coaches weren’t expecting him to be ready for the opener. Instead, Doolittle tied his career high with three tackles against Louisiana-Monroe.

“I didn’t think he would start playing until about this next game,” defensive coordinator Paul Rhoads said. “I really believed it was going to be somewhere around midseason before we could start counting on him. That he was ready to go in the first game and played as well as he played in the first game has been a tremendous asset to our defense this year.”

Sophomore Mike Blanc had started the first four games alongside Marks.

Auburn’s normally stingy defense gave up 132 rushing yards to LSU’s Charles Scott, and Doolittle wound up playing much of the game.

Doolittle was a Class 6A All-State pick and SuperPrep All-American coming out of nearby Opelika High School when he arrived in 2003. The 6-foot-3, 280-pounder was athletic enough to rush for 860 yards and 13 touchdowns as a senior while seeing limited action on defense. As a junior, he had racked up 50 quarterback pressures.

At Auburn, Doolittle was never able to work his way high up in the playing rotation, and pins the blame on himself. Now, he said, he is “a much better player.”

“I took a lot of things for granted when I was here. I kept putting it off, ‘I got next year,'” Doolittle said. “But this is my last go around, so I’ve got to make the most of it.”