Arias, who appeared in 42 games for the Astros last year and was expected to begin the season in the bullpen, hasn't pitched since leaving Houston's March 9 game against the Mets with shoulder discomfort. He underwent an MRI on Monday.
Astros general manager Ed Wade said on Tuesday that Arias will continue treatment, but he will likely be placed on the disabled list to start the season.
"He'll spend some time in the trainer's room trying to get the rotator cuff strengthened, but at this point, we're probably looking at a DL," Wade said. "I don't think it's going to be something that's going [to be] resolved in the short term, where it's something he's going to be pitching in games and [be] game ready. We'll cross that bridge when we come to it, but it's probably where we're headed at this point."
Major League Baseball's earliest retroactive date this year is Friday, meaning Arias would be eligible to return as early as April 10 -- a date that would put him out for the first four games of the regular season.
"We're going to take it day-to-day, but I wouldn't be sticking my neck out even to the probably point of view if I thought it was something that was going to resolve quickly," Wade said. "I think we're headed in that direction, but we'll remain hopeful that I'll be pleasantly surprised otherwise."
Arias, 26, went 2-1 with a 3.35 ERA in 45 2/3 innings last year for Houston and appeared in 22 consecutive games without allowing an earned run. He went on the DL on Aug. 28 with a right hamstring strain and finished the season on the DL after having arthroscopic knee surgery on Sept. 23 to remove bone fragments.
Arias' injury opens another spot in the bullpen entering the final stages of Spring Training. Right-handers Sammy Gervacio and Wilton Lopez are making a strong case for spots in the 'pen. Gervacio has struck out 11 batters and given up three hits and one run in nine innings, and Lopez has allowed three hits in six scoreless frames.
"To me, he's knee-deep in the mix," Wade said of Lopez. "He's got an outstanding arm and outstanding stuff and an outstanding future. He pitched two innings [Monday] and pitched as well as he did and showed he can go back-to-back innings. He's right in the competition with six or seven other guys right now."
Newcomers Matt Lindstrom and Brandon Lyon have bullpen spots locked up, with Jeff Fulchino, Tim Byrdak and Chris Sampson likely to make the club. Brian Moehler will make the team out of the 'pen if he doesn't win a spot in the starting rotation. Non-roster right-handers Gary Majewski and Casey Daigle are also in the hunt.
"It's been an area of strength during Spring Training, not only the roster guys but the non-roster invitees have stepped up and done a nice job as well," Wade said. "We hate not having Arias available, but at the same time, we have had several guys step up and perform very well."
Wade spoke with head athletic trainer Nate Lucero in Kissimmee, Fla., on Tuesday morning to get an injury update on first baseman Lance Berkman (left knee surgery), shortstop Tommy Manzella (strained right quadriceps), center fielder Michael Bourn (mild right oblique strain) and outfielder Jason Bourgeois (left hamstring strain).
Bourgeois is doing all baseball drills, except running, and Bourn isn't being allowed to swing a bat.
"It seems like everybody's progressing," Wade said. "Talking to Nate, sounds like Bourn and Manzella felt better today, and I saw Lance over there this morning and he said he was feeling better. He's progressing."
Brian McTaggart is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.