Make a rash decision and kill the player's confidence, and potentially lose the respect of his teammates who play next to him.
Make a move too late, and it might be too late to save the player -- and the team.
"You've got 25 different guys in there. You've got 25 different personalities," Manuel said. "Every one of them is different. How you handle them is completely different sometimes. It's a feel for when to sit a guy. It's a feel for how you treat him and how you try to help him if he's struggling or needs help. Sometimes it's showing him you believe in him and you're not really worried about him."
Manuel is showing his faith in Lidge, despite cries from concerned fans about his six blown saves.
There are reasons for Manuel's unwavering support.
First, Lidge has earned the right to pitch out of his slump. He went 48-for-48 in save opportunities last season, including the postseason. The Phillies don't win the World Series without him, and they very likely don't win the World Series again without him pitching like last season.
Second, Manuel sees that Lidge has thrown the ball well recently. He went 5-for-5 in save opportunities before he blew saves Friday and Saturday against the Dodgers at Dodger Stadium. And he would have been 6-for-6, except Pedro Feliz booted a ball with two outs in the ninth inning Friday.
Third, Manuel believes Lidge is the best man for the job. Sure, some fans have asked for Ryan Madson to temporarily fill the closer's role until Lidge corrects himself, but Madson has never closed and he has thrived in the setup role.
Lastly, pull Lidge from the closer's role and it could cripple his confidence.
Lidge lost his closer's job after he blew a few saves with the Astros early in the 2007 season.
"One save," Lidge pointed out.
Pulling Lidge that early sent a terrible message: the Astros have absolutely no confidence in you.
"When I lost that job in Houston, it was tough for a while," Lidge said. "I didn't know what was going to end up happening or anything else. It's unsettling. With Charlie, he talks to us. He doesn't say things that don't need to be said, but when things need to be said he'll talk to you. He'll say, 'Hey, you're not throwing the ball bad. You're getting hit here and there. You're getting some bad breaks here and there. That's why I'm still going with you.' It's nice for me to know that he knows that. It's nice to know that he'll stand behind me.
"That being said, in my line of work, results have to happen. But I'm hoping obviously we never cross that bridge."
Manuel didn't start Rollins on Saturday, and dropped him from first to sixth in the lineup Sunday.
Rollins hadn't hit lower than fifth in the lineup since May 25-26, 2006, when Manuel hit him sixth against the Mets at Shea Stadium and sixth against the Brewers at Citizens Bank Park.
Manuel dropped Rollins to sixth that season because he had hit just .196 (25-for-126) in his previous 32 games. It might have been a coincidence, but when Manuel returned Rollins to the leadoff spot May 27, he hit .304 in the next 28 games and .293 the remainder of the season.
Manuel made the move this time because Rollins had just two hits in his previous 23 at-bats, and his .249 on-base percentage as a leadoff hitter ranked last in baseball. Manuel needs to get Rollins going, and he felt Saturday and Sunday were the right times to make an adjustment.
He made similar moves with former left fielder Pat Burrell. If Burrell got into one of his lengthy slumps, Manuel would rest him for a day or two. It seemed the mental and physical breaks often helped.
Manuel has showed his touch elsewhere, too. He knew the right time for Jayson Werth to replace Geoff Jenkins as the everyday right fielder last season, although it helped that Jenkins missed time because of an injury. He knew when to elevate Madson into the setup role.
"You need guys to get the work in and slowly incorporate them into tougher and tougher spot," said reliever Chad Durbin, who also saw his role slowly elevated last season. "I'm pretty sure everybody is happy with how Madson turned out."
Manuel awarded right-hander Chan Ho Park the fifth spot in the rotation in Spring Training, and allowed him enough of a chance to prove himself in the rotation before ultimately pulling him for left-hander J.A. Happ, who has pitched much better.
This is not to say Manuel's moves always work. They don't. But when they don't, they at least don't seem to disrupt clubhouse chemistry. In other words, he carefully considers each move before he makes it, which his players seem to respect.
"He's very observant of what's going on in the clubhouse, on the bench, in the field, BP, all the activities," starter Jamie Moyer said. "It's an individual thing. Each individual deals with things in their own way, depending on what they're dealing with. But he does a good job trying to put his players in positions where they can succeed. If he's got confidence in me, why don't I have confidence in myself? It's that type of thing.
"It's a feel. It might be body language from a player. Maybe it's a feel from what he sees on the field. Maybe a guy needs a kick in the butt. Or maybe he just needs a day off. That's where his expertise comes in. I think his maturity, his age, his experience -- those are intangibles. Joe Torre. Tony La Russa. Jim Leyland. These are guys who have been around. They're touted as good managers, but they have some instinctual things inside them that they might not even be able to explain verbally. It's a sixth sense that you have."
It is a fine line, which makes Manuel's gut instincts important over the course of a 162-game season, plus seven weeks of Spring Training and a potential postseason.
"But there comes a point when a guy has to be understanding," Manuel said. "He has to understand what we're trying to do. We're trying to win the World Series again. We're trying to win games. If you walk right over there to ask [Chase] Utley why he comes to the ballpark every day, he'll tell you he comes to win. That's how I look at it. Believe me, we're going to do everything we can to win."
"But at the same time," Manuel said, "there's a time when you definitely stay with someone."