ARLINGTON -- Melvin Mora finally came clean regarding his left hamstring ailment on Monday, when he admitted that the injury has been bothering him since Spring Training and doesn't seem to be getting better. Mora had previously attempted to downplay the injury, but hasn't been able to hide its trajectory.

"It's getting worse and worse and worse," Mora said of the ailment. "It's something that I have to talk to the manager about. I need to heal the thing before I go back into the lineup. I've got to be 100 percent."

Mora characterized the injury as tightness in the muscle, and he said that it's kept him from being able to run or feel comfortable in the batter's box. The veteran said that he's not sure when he'll be able to play again and that he doesn't know if he'll require a stint on the disabled list. For now, he just wants to rest up.

"I didn't pull it," Mora said of the hamstring, which kept him out of a game last week. "It's just like every time I run, I feel like I have a baseball inside. It's kind of getting straight and I don't want to break it."

Baltimore manager Dave Trembley wouldn't say how long he expects Mora to be out, instead classifying the injury as day-to-day. The possibility exists that Mora will miss the entire Texas series, though, and Trembley said that he'll likely slot reserve Ty Wigginton at third base until his starter is ready to return to the lineup.

"We'll try to keep everybody else intact until Melvin comes back," Trembley said. "He told me yesterday, I guess, his second at-bat he felt his leg tighten. I wasn't going to put him in the lineup today after yesterday as a precautionary thing. Then when he came in today, I told him, 'Melvin, we should get this thing where it's 100 percent where we don't have to go back and forth. Let's not go back and forth, play one day, can't play one day.'

"I don't think that's fair to him and I don't think that's fair to the team."

Mora appeared to injure himself during his stint with Team Venezuela at the World Baseball Classic, but he hasn't been forthcoming about how it happened and the extent of the ailment. He has consistently received treatment for it for most of the spring and has had his hamstring wrapped both before games and practices.

One thing that is clear, though, is that Mora aggravated the ailment in the series finale against Tampa Bay.

"I was fine the game before and that day, the first groundball I hit off [James] Shields to third base, I tried to take off hard and that's when I feel it," he said. "It's not bad where I'm going to be out for three months. It just doesn't feel good. The second at-bat when Shields threw me the fastball, I wasn't able to step into it."