Dodgers’ Matt Kemp to be out at least four weeks

Slugger Matt Kemp will be sidelined at least four weeks after he suffered an additional injury to his left hamstring, Dodgers head trainer Sue Falsone said Thursday.

Kemp was playing in only his second game back from a 15-day stint on the disabled list when the center fielder hurt the hamstring again trying to score from first base in Wednesday’s game.

An MRI exam revealed “he has a little bit of swelling in the same area as well as a new strain in a different part of that hamstring,” Falsone said.

Both were so-called Grade 1 strains, meaning “there’s not a lot of muscle fiber tear,” she said. “It’s the lowest grade of muscle strain, so that’s good news.”

Asked about the best-case scenario for Kemp’s return, she replied, “About four weeks.”

Kemp initially hurt the hamstring May 5 in Chicago, felt the injury again May 13 in Colorado and then went on the disabled list the first time.

Manager Don Mattingly said “we thought [Kemp] was ready to roll” when he rejoined the team Tuesday, and Mattingly took notice of how Kemp broke a bat over his knee in frustration when the outfielder realized Wednesday that the injury was still with him.

“It hurt him,” Mattingly said. “It’s kind of touching the way Matt is . . . when you see a guy who wants to play that bad.”

Castellanos called up

Alex Castellanos, who was acquired by the Dodgers last year in the trade that sent Rafael Furcal to theSt. Louis Cardinals, was called up from triple-A Albuquerque to replace Kemp.

Mattingly said he planned to play Castellanos, 25, mostly in the outfield.

Castellanos also was sidelined by a hamstring injury for a month, but he returned to the Albuquerque lineup Saturday. He was hitting .379 with five home runs and 14 runs batted in.

Loney’s batting struggle

First baseman James Loney did not start Thursday because “it’s been a little bit of a battle” at the plate for him lately, Mattingly said.

Mattingly said he also wanted to give rookie Scott Van Slyke, who started at first base in Loney’s place, an opportunity to play.

Loney was batting .245 with two home runs and 15 RBIs. Although he had a three-hit game last Saturday, Loney had batted only .154 (4 for 26) in his last eight games.

Mattingly has sat the left-handed Loney against left-handed pitchers already this season, but this time right-hander Zack Greinke started for the Milwaukee Brewers.

Injury updates

Left-handed starting pitcher Ted Lilly, on the disabled list, will have an MRI exam Friday amid continued soreness in his pitching shoulder, Falsone said.

Second baseman Mark Ellis, who had emergency surgery on his left leg May 19, does not appear to need added surgery on the leg’s knee, Mattingly said.

Juan Rivera (left hamstring) and Juan Uribe (left wrist) continue to improve but do not yet have timetables for returning to action with the Dodgers, Mattingly said.

james.peltz@latimes.com