How long Dellucci, who was injured while attempting to beat out a throw to first in the bottom of the fourth inning, will be out was not immediately known.
"It's a DL situation," manager Eric Wedge said. "It's just a matter of how extreme it is."
Dellucci, still being treated in the trainer's room well after the game was finished, was unavailable for comment.
The injury will likely see Jason Michaels, who had been sharing time with Dellucci in left, become the everyday left fielder, and the Tribe having to call up a fifth outfielder.
The Indians' top two outfield prospects at Triple-A Buffalo are Shin-Soo Choo and Ben Francisco, both of whom have seen time with the big club this season.
Dellucci's injury occurred with runners on the corners in the fourth. Dellucci hit a grounder to Phillies first baseman Ryan Howard, who fired to second to get the force out.
Shortstop Jimmy Rollins tried to double up Dellucci at first, but Dellucci made it safely with a headfirst slide. He appeared to grab his left leg before making the slide, and, once safe, he immediately lay on the ground in pain.
Two members of the Indians' athletic training staff carried Dellucci off the field, as he put no weight on his left leg.
Dellucci is batting .234 with four homers and 19 RBIs this season.
David Briggs is an associate reporter for MLB.com. Anthony Castrovince contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.