Bell surrendered the tying run in the ninth inning at San Diego. The Marlins prevailed, 9-8, in 12 innings, with Steve Cishek working three innings.
Most likely, Bell will be used in the sixth or seventh inning in the short term.
"We're going to move him down for a few days to get him back on track," Guillen said Saturday afternoon. "It's not like we're removing him from his job. I made it clear to him that if we're going to be the club we should be, it's easier for him to be where he's supposed to be."
Circumstances will determine which inning Bell is used.
"Whatever inning we think will be the best for him," Guillen said.
With the Padres from 2009-11, Bell recorded 132 saves, the most in the Major Leagues. Last year, he converted 43 of 48 chances. Already, he has blown four of seven opportunities.
"I talked to Bell. We had a great conversation," Guillen said. "He understands my point. We are a better pitching club with him to be the closer. Right now, he's going through a rough time. It's a combination of making bad pitches to not catching any breaks. That's going to happen. It happens to the best."
Bell's velocity has been between 92-94 mph. It's not so much a dramatic drop in how hard he's throwing, his command has been off.
Steve Cishek is the frontrunner to pick up the closer role, but the right-hander threw three innings on Friday. He won't be available at least until Tuesday at Houston. Cishek has thrown five innings in three days.
On Saturday, Guillen was leaning toward using Ryan Webb or Randy Choate in the role.
Guillen added that the hope is Bell will gain some confidence and success in the earlier innings, and he will then go back to pitching the ninth.
Demoting an All-Star player, Guillen said, is one of the hardest moves for a manager.
"I made it very clear," Guillen said. "This is not a punishment thing, this is about helping [Bell] and the ballclub."
Cishek has the makings of being a closer for the long term. He will get his chances once he is ready to pitch again.
"This kid can be a closer very soon," Guillen said of the 25-year-old. "We have one for a couple of years. He's got enough stuff to be a closer."