Towles said he didn't feel any sort of pop when the injury first occurred. Comparing it to a right hamstring injury he had two years ago in Class A Lexington, the catcher said this one wasn't as bad.
Towles hopes this injury will sideline him for only a short time.
"I think it will be just a couple of days, no more than four or five days," he said. "I don't know. They might try to take it easy on me, but I want to get back out there as quick as possible, that's for sure."
Towles, 24, is the leading candidate to win the No. 1 catching job this season. Defensively sound Humberto Quintero is also in the running, with Brad Ausmus slated to serve as the backup.
Towles was hitting .538 (7-for-13) with two doubles, one homer and five RBIs over six Grapefruit League games at the time of his injury. Minutes after he suffered the strain, he had already started to think about the worst-case scenarios.
"You've got to come in here and prove that you're ready for the starting role," he said. "Whenever something like this happens, it just sets you back. So now, you're wondering if they're thinking they should just send me down for rehab or just send me down to Triple-A just to see what I can do. All that runs through your mind. You've just got to trust God. Things happen for a reason."
Felipe Paulino is not considered a front-runner for the fifth-starter spot, but a good spring could change his manager's mind.
The right-hander's outing on Saturday probably did little to sway Cecil Cooper. On a windy day at Osceola County Stadium, players had to deal with 35-mph gusts out toward right field. This didn't help the pitchers, including Paulino, who yielded home runs to Luis Jimenez and Ronnie Belliard.
Paulino also issued four walks.
"I was behind the count and trying to put the ball over the plate," he said. "When you get behind in the count, you can't use your pitches. You've got to come back with your fastball. If you're ahead in the count, you've got an opportunity to get outs. Today, that wasn't what happened with me."
Cooper agreed. He was pleased with Sammy Gervacio and Mike DeJean's outings, but overall, the skipper wasn't impressed with the effort of the pitching staff, which issued 10 walks.
"All you look for there is command and that kind of stuff," Cooper said. "I didn't see much command today. I think Paulino threw well, but his command -- he was behind in the count a lot."
Fernando Nieve, who has been sidelined for most of the spring, threw a bullpen session on Saturday.
"He got through it OK," Cooper said. "It was a good session. I know I stood there for a good 10 minutes watching him throw."
The Astros' 25-man roster is pretty much set, with only one rotation spot and maybe two bullpen spots still up for grabs.
Shawn Chacon still appears to be the front-runner to nab the final spot in the rotation, although Cooper emphasized that all 11 pitchers being stretched out this spring are still in the running.
"The only guy you've got to think time is slipping a little bit is Nieve, just because he was hurt," Cooper said. "Everybody's still there -- still in, and getting their turn."
The pitchers who are either locks for the rotation or are competing for a job are Roy Oswalt, Brandon Backe, Wandy Rodriguez, Woody Williams, Chris Sampson, Chacon, Runelvys Hernandez, Jack Cassel, Mark McLemore, Paulino and Nieve.
Cooper surmised a large bulk of the pitchers could see the competition go down to the wire.
"Even if there's one or two who might get weeded out, we're still going to have to go a while," Cooper said. "I would think at this point [Chacon is] the front-runner. Technically, we've got two spots. You've got to give Woody the edge at this point for the other one, but that's all subject to change, depending on what happens."
Up next: The Astros will travel to Port St. Lucie, Fla., to play the Mets on Sunday at 1:10 ET. Right-hander Jack Cassel will start for the Astros, who will face Mets righty John Maine. Houston rotation hopeful Runelvys Hernandez will also pitch in the game.