BOSTON (CBS) –  Daisuke Matsuzaka is set to make two more minor league rehab starts before rejoining the Boston Red Sox.

His new manager is hoping he works out a few issues before then though.

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“I didn’t think he was as good as he should be,” Valentine said of Matsuzaka’s latest outing on Saturday. “His mechanics weren’t very good at all. But he’s throwing pain-free, so that’s good.”

Matsuzaka was not sharp in his fourth rehab outing Saturday for the Pawtucket Red Sox, allowing five runs off seven hits, including two homers, over 5.1 innings pitched. He walked just one while striking out five, with 54 of his 90 pitches going for strikes.

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“Right now he’s worried about his strength and his ability to endure pitches, things like that. He’ll take another step,” Valentine said on Sunday.

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Matsuzaka will toe the rubber for the PawSox on May 17 and 22, and then will come decision time for Valentine and the Red Sox. With their five-man rotation already set with Jon Lester, Josh Beckett, Clay Buchholz, Daniel Bard and Felix Dobrount. While each have had their problems, it will be hard for Valentine and the Sox to work Matsuzaka into the mix when the time comes.

How does Valentine feel about a potential six-man rotation?

“A full-time six-man rotation? It depends who the six are,” said Valentine. “I guess it can work but I don’t have any plans for that right now as a long-term situation. I can see it being done a couple of times through out of necessity.”

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One thing Valentine is hoping comes out of Matsuzaka’s impending return is a little competition from those already in the starting five.

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“No one has asked me about his situation as it relates to their situation, but I hope everyone in the starting staff feels like they have to compete and earn everything they get,” Valentine said.