Lee has a fracture of the distal radial and the distal ulna bone in his hand. He will wear an immobilizing cast that will go past his elbow. Team officials won't speculate on how long Lee will be sidelined, but he could be out two to three months.
The defending National League batting champ was injured late Wednesday in a freakish collision at first base with Dodgers shortstop Rafael Furcal.
"Obviously, he's going to be out a while and he's a good player," Cubs general manager Jim Hendry said Thursday of Lee. "I'm sure he's devastated today because he's a total team guy who's integral to what we want to accomplish."
Hendry said the team had yet to decide on who to call up from the Minor Leagues to replace Lee on the roster. Among the candidates to be considered are infielders Ryan Theriot, Brandon Sing and Michael Restovich. John Mabry and Todd Walker could sub at first base for now.
"We'll make a decision [late Thursday] on who we want to add to the roster in an in-house move," Hendry said. "You're not going to replace Derrek Lee in any kind of trade in April. You're probably not going to replace him anytime in a trade as hard as you might try."
Lee had flown back to Chicago to be examined by the team's medical staff and a hand specialist. The Cubs open a three-game series against the St. Louis Cardinals on Friday.
"It's a big blow, so we have to keep plugging and hope we can play better and better," Hendry said.
The Cubs have had their share of injuries. Last season, Walker, Nomar Garciaparra, Aramis Ramirez, Kerry Wood and Mark Prior missed significant time because of different aches and pains. Wood, Prior and Wade Miller are currently on the disabled list with shoulder injuries. Outfielder Angel Pagan was placed on the 15-day DL on Sunday with a tear in his left hamstring.
Lee was injured in the Dodgers' seventh on Wednesday. Furcal led off the inning with a bunt single to the right of the mound, and reliever Scott Eyre dove for the ball before flipping it toward first base with his glove.
The ball sailed over Lee's glove as Furcal collided with the first baseman at the bag.
Eyre suffered a bruised right knee on the play, and his status was day-to-day.
"You never see anyone lose two guys on one play," Cubs manager Dusty Baker said after the game. "But nobody cares if Lee's hurt or not except us and the people in Chicago and the people who know him. We'll just have to adjust and just keep on adjusting."
Lee has appeared in no fewer than 155 games in any of his previous six seasons, and has never been on the disabled list. Last season, he batted .335 with 46 homers and 107 RBIs and played in his first All-Star Game.
He was hitting .318 in 14 games with three homers and 10 RBIs, and had signed a $65 million, five-year deal on April 11.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.