Mark Appel struggled with Class A Lancaster in California during extended spring training, something Jeff Luhnow blamed on the pitcher's overall adjustment to professional baseball.

The Houston Astros use a tandem system, where eight pitchers work in pairs over a four-game rotation.

Appel was accustomed to pitching once a week at Stanford. He threw only 38 innings in Houston's system after signing last season, essentially pitching once a week again.

"It was really my fault," Luhnow said. "I made a decision to send him out to Lancaster to have him try and build up there, to try to catch up for the time he missed in Florida. He ended up pitching twice on a four-day cycle and then he skipped a start and pitched on an eight-day cycle. It wasn't like he was in the tandem for a month and couldn't handle it.

"I happened to be there last week. I watched his start. I talked to him afterward. You could just tell he was not in the flow of pro ball, irrespective of five-day, four-day, six-day. He hasn't gotten conditioned to throwing and resting, throwing and resting, the way you need to get conditioned in order to be in a five-man rotation, much less a four-man."

The Astros decided to take Appel "off the grid," away from the media, away from the hitter-friendly Lancaster environment.

"I don't expect this to be more than a couple of weeks," Luhnow said. "Really, it's just to make up for spring training. It's my fault for sending him to Lancaster. I thought he could do it there. But once I started to think back on the history of what happened, I realized that he just didn't have a proper spring training."