PITTSBURGH -- The Astros weren't anticipating such a drastic measure in regard to Kazuo Matsui's strained right hamstring, but after four days of waiting, it was clear that only one option was viable.

Matsui was placed on the 15-day disabled list after Friday night's 6-1 win over the Pirates. The move is retroactive to Tuesday, the day after Matsui last played.

"He just wasn't any better," manager Cecil Cooper said of Matsui's workout on Friday -- the day the team had anticipated having him back following Thursday's off-day. "We were hoping he'd get to be better, but he just wasn't any better than he was a couple days ago. We thought two days would make him pretty good, but it just wasn't. We'll give him the next week to 10 days off, and hopefully, he'll be all right."

The team purchased the contract of utilityman Matt Kata from Triple-A Round Rock, and he will take Matsui's place on the active roster.

Matsui, 33, was hitting .219 with one home run and 12 RBIs this season.

"The last four days, it was getting better, but I ran today and I felt like it was like 40 percent," Matsui said through an interpreter.

Kata, 31, was hitting .277 with two home runs and 14 RBIs for Round Rock. He has played second base, third base, shortstop and the outfield over his professional career.

In 238 Major League games with the Diamondbacks, Phillies, Rangers and Pirates, Kata has a .242 average with 12 home runs and 58 RBIs.

"He can play multiple positions, he's a switch-hitter and he was with us all spring," Cooper said. "He did a good job for us."

Cooper said that he will "mix and match" whom he plays at second base in Matsui's stead. Rookie Edwin Maysonet went 4-for-4 with a home run and four RBIs there on Friday night. Kata, along with veterans Geoff Blum and Jeff Keppinger, are also possibilities when they are not playing at third.

"We're just going to mix and match like we've been doing," Cooper said. "But right now, sure, I've got to write [Maysonet] out there tomorrow, for sure."