PITTSBURGH -- The Penguins say center Evgeni Malkin is out indefinitely with a lower-body injury.

The team placed the Russian star on injured reserve Thursday, two days after Malkin appeared to hurt his right knee in a loss to the Boston Bruins.

Head coach Mike Sullivan described Malkin as "week-to-week."

Malkin was playing his best hockey of the season when he collided with Boston defenseman Jarred Tinordi late in the first period of what became a 2-1 loss to the Bruins.

"When you lose [Malkin], it's a tough loss from our standpoint for everything that he brings to our team," Sullivan said Friday. "We're certainly encouraged that we'll hopefully get him back in a timely fashion."

Malkin has eight goals and 16 assists and put together an eight-game point streak from March 2 to March 15 before getting hurt.

Evan Rodrigues filled in for Malkin on the second line in a loss to New Jersey on Thursday night. There's a chance Jared McCann, who has missed the last five games with an injury, could center the second line on Saturday in New Jersey. McCann skated with the second line in practice on Friday.

The Penguins entered Friday in third place in the highly competitive East Division.