HOUSTON -- Kaz Matsui handled the news of his release with the kind of professionalism the Astros had come to expect from the veteran second baseman during his nearly 2 1/2-year stint at Minute Maid Park.

The Astros announced Wednesday they would ask for waivers on Matsui for the purpose of giving him his unconditional release and likely eating the remainder of his three-year, $16.5 million contract that was set to expire after this season.

The move didn't come as a surprise considering Matsui was hitting .141 with one RBI in 27 games this season, including an 0-for-20 slump he carried into Wednesday. The club purchased the contract of infielder Oswaldo Navarro from Triple-A Round Rock.

"I couldn't make a good result," Matsui said through interpreter Yoshitaka Ono, following Wednesday's 7-3 victory over Colorado, the team Matsui helped reach the World Series in 2007. Ono was also let go, and massage therapist Katsumi Oka was given the chance to remain with the team.

"I spent two years and a half here and I was a free agent and I [signed with Houston so I] could be on a great team with great fans and I could play in a good environment with good teammates and a good city," Matsui said. "I had a really good time and it's been my pleasure."

Astros manager Brad Mills said Jeff Keppinger would be the starting second baseman. Keppinger had all but wrestled the starting job away from Matsui, but Mills resisted labeling him the starter until now. Keppinger went 3-for-5 with two doubles and a career-high four RBIs on Wednesday.

"I'm looking forward to it," Keppinger said. "That's why I'm here. I've always looked at myself as a second baseman and I've always tried to be able to be a starter. I don't know if they've named me a starter or what, but they keep running me out there and batting me in the two hole. That's fine with me. That's why I'm here."

Houston general manager Ed Wade, who signed Matsui to replace franchise icon Craig Biggio following the 2007 season, said Matsui is making roughly $6 million this season. The Astros will be on the hook for the remainder of the contract unless he's claimed off waivers. If he signs with another club as a free agent, that club would pay him the prorated minimum, with the Astros picking up the rest.

"Obviously it's never easy to talk to a player at this point in the season about an unconditional release, particularly somebody who has conducted himself with the level of professionalism that Kaz has here," Wade said. "We respect the way he went about his business and unfortunately this year and parts of last year his performance hasn't been quite what he expected or what we saw when he hit .293 in 2008."

Matsui performed well in his first season in Houston in 2008, hitting .293 with six homers and 33 RBIs. But he only played in 93 games, thanks to three stints on the disabled list, including once for a lower back problem that was an issue his entire time with the Astros.

He had his healthiest season in the Major Leagues last year and appeared in a career-high 132 games, but he hit .250 with nine homers and 46 RBIs.

"We really felt the way he performed in 2008 was sort of a mirror of the performance we saw in 2007, when he was so good with Colorado," Wade said. "Last year a succession of the back issues coming up from time to time, it was a struggle. This year was a significant struggle for him. If we were firing on all cylinders at other positions this would be something we would push to the backburner, but we felt it was important for us to do it at this time."

Matsui was a seven-time All-Star in his native Japan (1997-2003) and was a career .309 hitter with 150 homers and 616 RBIs in nine seasons in Japan.

"He worked hard every day and did everything he could, but we just wish it could have worked out better but it didn't," Mills said.

Navarro, 25, entered Wednesday hitting .312 with four doubles, one triple, three homers and 19 RBIs at Triple-A Round Rock. He had appeared in 14 games at shortstop and seven at second base after being signed to a Minor League contract in December.

Prior to signing with the Astros, Navarro spent his entire eight-year pro career with the Mariners, who signed him as a non-drafted free agent in 2001. He has appeared in four Major Leagues, going 2-for-3 in 2006.

"Ozzie's playing very well for Round Rock right now, and we know he can play second, we know he an play shortstop," Wade said. "Even though he's been in pro ball for what seems like forever, we know there's an upside with Ozzie that we can take advantage of. It's up to Millsie how he wants to mix and match, but certainly Keppinger's performance from the very first day of the season has been very solid and gives us comfort at the position."