HOUSTON -- Astros relief pitcher Brandon Lyon acknowledged late on Wednesday he could be headed for surgery after being placed on the disabled list earlier in the day for biceps tendinitis, the same injury that put him on the shelf for a month earlier this season.

Lyon is scheduled to travel to Los Angeles and be examined on Friday by renowned orthopedic surgeon Lewis Yocum. The Astros called up left-hander Fernando Abad from Triple-A Oklahoma City, and he will join the club on Thursday.

"There's definitely some issues in my shoulder right now, and [surgery] is definitely an option," Lyon said. "I want to get a grasp on it, and talk to other people and get their opinions on it, and just move forward after I hear what they have to say."

Lyon, who was Houston's closer to start the year, has struggled all season, posting an 11.48 ERA in 15 games, and had allowed a home run in each of his three outings since being activated on Friday from the disabled list, where he was for 32 games with biceps tendinitis and a partial tear of the rotator cuff.

"It's obvious, he's been struggling from a performance standpoint," Astros general manager Ed Wade said. "I talked to [manager] Brad Mills and [head athletic trainer] Nate Lucero last night after the game about whether we thought he was [OK] physically, and we had a chance to sit down with Brandon this afternoon and he admitted he still has discomfort in the biceps tendon.

"It doesn't make any sense for him to go out and try to be a hero. And with the way he's feeling right now, we're going to put him on the disabled list."

Lyon said it was "killing" him not to be playing, but he understands he has to be healthy to be effective, and said the time is right for a second opinion.

"Obviously, I'm not too excited about it. But the best thing right now is to get to the source, and get everything figured out so I can get healthy," he said. "It's hard to decide if you're a little bit banged up or you're really hurt. I've pitched through things before, so it's hard for me to decide if it's some painful stuff I can throw through or not. Right now, it's time to explore other options and get different opinions, and get this squared away so I can help this team."

Yocum, team physician for the Los Angeles Angels, is often a pitcher's last stop before having arm surgery. But Wade is hopeful.

"I think it was in Brandon's best interest, and our best interest, to try to handle this conservatively. And hopefully, that's the message that we get when he goes through the next series of examinations," Wade said. "I think this is a little bit of a case of Brandon wanting to help the club, wanting to get to the point he was a year ago -- where he saved 19 games the second half of the season. He's just been physically unable to perform at the level he has been in the past."

In 2010, Lyon posted a 3.12 ERA in 79 games, with 20 saves -- allowing 68 hits in 78 innings. His 19 saves after Aug. 1 were tied for tops in the Majors with Mariano Rivera, and his two home runs allowed gave him the third-lowest ratio among all MLB relievers (trailing Jonny Venters and Carlos Marmol).

Abad, who had a 2.84 ERA in 22 games last year with the Astros in his Major League debut, was 1-1 with a 3.55 ERA in 11 games at Oklahoma City, striking out 16 batters in 12 2/3 innings. He started the season with the Astros, but was sent down after going 1-4 with a 7.43 ERA in 22 appearances.

"We talked to the Triple-A staff ... and we just about went through all the pitchers," Mills said. "[Jeff] Fulchino, we sent him down [earlier this week] to work on some things. He threw two pitches last night and got hit with a one-hopper and had to come out of the game. I don't think that's fair to him [to bring him back]. As we went through the other pitchers, we felt Abad was the best choice. The response to our questions were he's throwing pretty close to what he was last year."