One factor is how Junichi Tazawa fares in his Saturday start against the Yankees. It seems likely that Thursday's start will go to either Tazawa or Penny.
Penny declined comment before Saturday's game, saying he had to stretch and that "I don't know anything anyway."
In Wakefield, the Red Sox get the type of stabilizing veteran presence that the rotation has desperately lacked of late behind the dominant 1-2 tandem of Josh Beckett and Jon Lester.
In the first half, Wakefield went 11-3 with a 4.31 ERA.
"I don't know if I could have done any better than anybody else. You always question that," Wakefield said. "It is what it is. I'm glad to be back, and hopefully I can contribute as much as I did in the first half."
The biggest question mark surrounding Wakefield of late centered on his ability to field his position. But all sides seem confident that he'll be able to get the job done without risking further injury.
"We want him to be able to help us win," said Francona. "I think we felt like, arm-wise, he was probably better then he'd been, because he had a little bit of a rest. And it was fun to watch him pitch. You kind of think, 'Boy, he could sure help us.' At the same time, if he can't cover his position and you're putting him at risk of hurting himself -- first of all, it's not fair, and it's hard to win a game."
As a proving ground, Wakefield pitched twice for Triple-A Pawtucket, capped by Friday night's strong performance, in which he gave up two hits and a run over 5 2/3 innings.
"I think he really improved enough in yesterday's outing," Francona said. "And again, there should be some improvement before he pitches again [to the point where] everybody thinks he can pitch and win, and that would be the idea. Again, I don't think he's going to win a track meet. I don't think he was before, but he can cover his position and he's a really good pitcher, so I think we're OK."
After turning in such a strong first half, Wakefield's patience was tested by the injury that started nagging at him right after the All-Star break.
"This hasn't been an injury you could get a shot for or take medicine for and it's going to get better quicker," said Wakefield. "It was just a matter of the body healing itself, and getting my strength was the biggest hurdle I had to overcome."
In other pitching news, the Red Sox purchased the contract of right-hander Enrique Gonzalez from Triple-A Pawtucket to replace prospect Michael Bowden, who was hit hard by the Yankees in what wound up being his second one-day roster stint of the season. Gonzalez pitched for the Red Sox on Aug. 8 at Yankee Stadium, giving up three hits and two runs over 1 2/3 innings.