Lester will make his next start on Saturday at Yankee Stadium.
Before that, Lester will try to regain his form during a side session on Wednesday that might even include throwing to some hitters.
The Red Sox already have hitters lined up to face rehabbing closer Andrew Bailey that day.
"We've got a nice proactive plan," Valentine said. "He's going to throw Wednesday -- maybe throw to a couple of hitters, get a little feel for a couple of his pitches. He says he feels great. He's throwing the ball as well as he's thrown the ball in a couple of years. We've just got to get him to a point where his good stuff is getting hitters out. He says he's ready to do that."
Whenever a pitcher like Lester struggles, there is speculation about injuries. The Red Sox continue to say the lefty is healthy.
"No, he's not hurt, that's for sure," said Valentine. "He says he feels fine."
With the Red Sox having an off-day on Thursday, they would have been able to start Aaron Cook, Felix Doubront and Clay Buchholz for the series in New York and give Lester more time to regroup.
But the Red Sox decided to keep him going, just like they did with Buchholz when he was in a similar slump earlier in the season. Buchholz recovered nicely. Now the hope is that Lester will do the same.
The one thing Valentine seemed most concerned with was doing everything he could to help Lester stay confident.
"Well, just let him know that if you're that far down, there's only one way to go and that's up," Valentine said. "I believe in him. Nobody [in the media] does, but I do. So that's a good start."