OAKLAND (AP) — Brett Anderson is back from Tommy John elbow ligament replacement surgery, and set to make his season debut Tuesday night against the Minnesota Twins.

The left-hander was activated from the 60-day disabled list Monday, ready to pitch in the major leagues again for the first time since undergoing surgery 13 months ago.

“You just have to go out there and be a competitive player and be a competitive person,” Anderson said of his approach. “You can’t go out there and worry about mechanics and can’t go out there and worry about your elbow.”

Oakland optioned right-hander Dan Straily to Triple-A Sacramento and cleared room on the 40-man roster for Anderson by designating catcher Anthony Recker for assignment.

The 24-year-old Anderson has lost more than 20 pounds from his previous playing weight of 248 — and noticed he felt stronger late in games during his minor league rehab appearances.

He is eager to get back into a regular routine preparing for starts every fifth day. That’s what he is most used to, not the long process of rehabilitating and physical therapy that has defined his life over the last year.

“Yeah, it’s been a while,” he said. “Baseball players are so routine-based, and I’m obviously superstitious and stuff. You kind of lose that a little bit over the course of a year, ‘All right, what do I do at this time? What do I do at this time to get ready?’ It’s definitely felt like it’s been a while. Hopefully it’ll all be worth it tomorrow and here on out.”

Anderson, a second-round draft pick by Arizona in 2006, went 7-6 with a 2.80 ERA in 19 starts during 2010, then 3-6 with a 4.00 ERA in 13 starts last year.

He hasn’t pitched in the big leagues since June 5, 2011, at Boston. Anderson probably won’t go further than about 100 pitches initially, though he showed no signs of fatigue or problems during a six-start rehab schedule with Class-A Stockton and Triple-A Sacramento. Anderson will try for his first major league victory since May 26 of last year at the Angels.

“He has thrown up to 90-something pitches and been down through the full complement. His bullpen was great the other day,” manager Bob Melvin said. “We feel like this could be a nice little shot in the arm for us.”

Anderson realizes he must earn and keep his spot in the rotation, too. Oakland is in a pennant race as the season nears its final month.

“I want to go out there and pitch well because we need to win ballgames,” he said. “So it’s going to be that much more pressure filled, but I wouldn’t have it any other way.”