Byrdak, 36, had appeared in 13 games and was 1-0 with a 5.23 ERA, but he said during the past three or four outings that he didn't feel he was getting through the extension side of home plate during his delivery. As a result, his breaking ball has been about 78-79 mph, which is down from the 81-84 mph he threw last year routinely.
"I'd rather go ahead and get some time now, and since we're early in the season, get it right and finish strong for the rest of the year instead of possibly going out there and blowing the shoulder or elbow out," Byrdak said. "I'm too late in my career -- if I have an injury like that, my career is over."
Byrdak was the only Astros relief pitcher to stay healthy for all of last season, appearing in a club-high 76 games.
"That's one of the frustrating things about it is that it bothers me enough to be effective out there, but it's still not quite enough where I can't pitch," Byrdak said. "I can pitch, but I'm not the same person I am. I need to be the same person I was last year.
"I took a lot of pride in the fact that last year I was the only guy that didn't go on the DL the whole course of the year and pitching almost 80 games, and I wanted to build on that. This is something that came up, and we felt the need to take care of it now."