Starter Chad Billingsley is expected to return to the rotation Tuesday against the Cardinals, Torre said.
Haeger, 25, was called up from triple-A Albuquerque last week. First drafted by the Chicago White Sox in 2001, he has appeared in only 19 major league games, with one start.
He was 11-6 with a 3.55 earned-run average in 22 starts with Albuquerque.
"We'll tentatively schedule him for Monday" but that could change "in the event we run into trouble here" and Haeger is needed in relief, Torre said before the Dodgers' game with the Arizona Diamondbacks.
Haeger was called up mainly "as insurance at the back of the bullpen" but with the idea that he could pitch more than an inning or two if needed, Torre said.
Reliever Jeff Weaver had filled a starting spot in the Dodgers' rotation last week against the San Francisco Giants, but "I don't want to pitch Weaver again because we need him in the bullpen," Torre said.
Weaver had started after Billingsley suffered a strained left hamstring, but Billingsley has shown improvement in his exercises and pitching practice, Torre said.
An hour before Torre's announcement, Haeger said he was "anxious to get in a game and help the team any way I can."
Haeger, a native of Livonia, Mich., said he developed his knuckleball five years ago.
"When I first was drafted I was just a regular right-handed pitcher," but within a few years "I couldn't get anybody out, so I had to figure out something," Haeger said with a chuckle.
"I always could throw them when I was a kid, kind of messing around," he said.
In 2004, he showed it during bullpen practices "to let the White Sox know I could throw it a little bit, and they said 'Give it a shot,' and here I am."
"It's something obviously they don't see very often," Haeger said of NL hitters. "A lot of guys don't know how to approach hitting it, so that's an advantage for me."
Torre noted that Haeger, who throws a fastball and occasional slider, is "not a predominant knuckleballer" like Wakefield and throws his other pitches with more frequency than Wakefield and former notable knuckleballers such as Phil Niekro.
Regardless, Haeger said he has already thrown his knuckleballs in practice with Dodgers backup catcher Brad Ausmus "and he handled it fine, and I'm assuming Russell [Martin] can handle it just fine too."
Martin and first baseman James Loney were not in the starting lineup Saturday, replaced by Ausmus and Mark Loretta, respectively. Torre noted that Ausmus had a higher batting average than Martin (.345 versus .263) against Saturday's starter, Doug Davis. . . . Tom Lasorda was to be inducted into the Brooklyn Hall of Fame today.
When: 1 p.m.
Where: Chase Field, Phoenix.
On the air: TV: Ch. 9; Radio: 790, 930.
Update: The Dodgers conclude their three-game series with the Diamondbacks, with Wolf hoping for a repeat of his last start, when he gave up only one run in eight innings in the Dodgers' 9-1 win over San Francisco on Tuesday. Wolf is 7-3 lifetime against the Diamondbacks. Petit, meanwhile, is 0-2 lifetime against the Dodgers with a 4.50 earned-run average, including a loss April 11 when the Dodgers beat Arizona 11-2 at Chase Field.
-- Jim Peltz