"If we think we can improve the club, we will," said Colletti.
Although he has added Josh Beckett and Joe Blanton this month, the apparent loss of Chad Billingsley and Ted Lilly leaves the Dodgers exposed should another starting pitcher fall.
"I think with us, we're always willing to add," Dodgers manager Don Mattingly said.
Billingsley has been shut down since injuring his elbow Friday night, which wasn't the case when he went on the disabled list after the All-Star break. He said he expects to have a contrast MRI at the end of the week when the inflammation subsides and receive a definitive diagnosis, but the club is not expecting good news.
Lilly, trying desperately to return from shoulder problems since late May, injured his back lifting weights on Sunday.
"He didn't look good," said Mattingly, whose playing career was shortened by back problems.
Meanwhile, Matt Guerrier is expected to rejoin the club when rosters expand after missing four months with elbow tendinosis.
And infielder Jerry Hairston has surgery set for Sept. 7 to repair an impingement and torn labrum in his left hip. The surgery will be performed in Vail by Dr. Marc Philippon, who will repair the tear in the joint and shave the head of the femur, which causes the tear. Hairston will have a rehab of three to six months.
"After doing a lot of praying and gathering information, I decided to have surgery," Hairston said. "Even though the desire to play is overwhelming, I can't put my own interests ahead of my teammates, the staff, the Dodgers organization or fans. I will enjoy watching my teammates' success and hopefully pour a lot of champagne. Go Dodgers."