So when he is not throwing well, maybe when he is not feeling confident, he has been throwing his slider.
He threw 18 sliders and just four fastballs on Wednesday in a 7-6 loss to the Marlins at Land Shark Stadium, where Lidge blew his Major League-leading 11th save of the season.
"His slider effectiveness revolves around his fastball command," Phillies pitching coach Rich Dubee said before Saturday's game against the Brewers at Miller Park. "You've got to throw that for strikes."
That is why Lidge threw 12 fastballs and just four sliders Friday in an 8-4 loss to the Brewers. Dubee thought Lidge took a big step forward, despite the fact he gave up a run. Lidge maybe could have gotten out of the inning without giving up a run had he thrown a few more sliders, but that wasn't the point.
"He was out there to throw more fastballs," Dubee said. "He threw four first-pitch strikes with fastballs. When was the last time he has done that? He threw 12 fastballs and nine were strikes."
Go back to Wednesday. Lidge threw a 2-2 fastball inside to John Baker with a runner on third and one out. The pitch was a ball, but it was a pitch that Baker had no chance to hit because the pitch never concerned him. He was looking slider all the way.
Lidge threw a 1-1 fastball inside to Hanley Ramirez with a runner on third and two outs. Dubee thought it was a strike, but it was called a ball. But it was close and Ramirez still had not even bothered to lift up his front foot to begin his swing. He also wasn't bothering with the fastball. Lidge threw a 2-1 fastball to Ramirez that might have been a little low, but it got called a strike. Once again, Ramirez had no intentions of swinging at the pitch.
"He was not concerned with the fastball," Dubee said.
Two sliders later, Ramirez walked to put runners on the corners with two outs. Lidge threw two sliders to Jorge Cantu, who singled to score the tying run, and three sliders to Brett Carroll, who singled to score Ramirez to end the game.
Ideally, Dubee said he hopes the Phillies get a big lead sometime in the next day or so and Lidge can continue to work on his fastball location. If he returns to the closer's role, he obviously would throw more sliders, but hopefully not at the clip he threw them Wednesday.
But Lidge's lost command of his fastball has been a mystery this year.
"You don't know if it was because of the knee factor. He was slow coming out of Spring Training," Dubee said. "There are a lot of issues."
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.