HOUSTON – The Astros placed second baseman Kazuo Matsui on the 15-day disabled list with an irritated disk in his back Saturday and purchased J.R. House's contract from Triple-A Round Rock.

Matsui left Tuesday's game against San Francisco with a sore back and will go on the DL for the third time this season. He missed the first 16 games while recovering from surgery to repair an anal fissure, then sat out 15 games after straining a hamstring in June.

The 32-year-old Matsui is hitting .285 with 19 stolen bases and 28 RBIs in 85 games this year. He had appeared in every game since coming off the DL on July 8, and Houston manager Cecil Cooper acknowledged that he might have overused him.

“I learned a valuable lesson,” Cooper said. “I was pushing the envelope a little bit, (because) he was playing well. He was kind of our igniter and you kind of hate to take a guy out like that. I kick myself for it a little bit.”

The 28-year-old House was hitting .303 with 17 homers and 55 RBIs in 119 games for Round Rock. He made 69 starts at first base and 36 at catcher, but Cooper said he'd use House off the bench until Matsui returns.

Cooper said House would be available against Arizona on Saturday night.