Matsuzaka, who is coming off two disappointing outings, will take the ball on Friday night when the Red Sox open a seven-game road trip in Toronto.
"He looked real good," Valentine said. "Talked to him today, think we might have found something that feels good about him."
When asked to elaborate, Valentine indicated it was a mechanical adjustment.
"Yeah, a little thing out of the stretch that he felt better about," Valentine said. "His command wasn't good out of the stretch the other day. Hopefully his command will be better next time."
Valentine has also decided to stick with lefty Felix Doubront, who is currently at a career-high 134 2/3 innings.
Doubront will pitch the finale of this three-game series against the Yankees on Thursday.
"Felix looks good and feels good -- absolutely," Valentine said.