Malkin has missed the past five games -- as well as All-Star Weekend in Raleigh, N.C. -- with a knee injury and a sinus infection. He has 15 goals in 42 games this season.
Letestu was injured during the morning skate Tuesday prior to the Penguins' 4-3 shootout victory against the Rangers in New York. Coach Dan Bylsma said Thursday that the injury involves his meniscus.
Bylsma also said that Crosby, who has missed the past 11 games with a concussion, will take a few days away from the team to visit his parents while continuing his rehab.
But that should not be construed as a setback in his comeback from a concussion.
"No, still continuing his functional rehab," Penguins general manager Ray Shero told ESPN.com via e-mail Thursday. "He doesn't need to be in Pittsburgh to do it. It's just to get away with the family for a few days."
Shero also confirmed that Crosby has been placed on long-term injured reserve (LTI) retroactive to Jan 5, so he can come off at anytime as you have to be out 10 games and 24 days (which he has been) to go on LTI.
It gives Pittsburgh cap room for calling up players due to Penguins injuries.
The Penguins are 2-0 since returning from the All-Star break, and have won four straight overall.
Information from ESPN.com's Pierre LeBrun and The Associated Press was used in this report.