Rask, who had surgery to repair a torn labrum in his right hip last July, has allowed five goals twice in the four games he's started this season. He also gave up five on 12 shots to the Carolina Hurricanes and was pulled after the first period in a 7-1 loss on Jan. 18.
"You're a proud player," Rask said. "You're trying to set your expectations high, but the reality sometimes doesn't match it. Obviously, I haven't been good enough. … Not satisfied, obviously."
Rask signed a one-year, $1 million contract with the Bruins on Jan. 11. The intention was to send him to Providence of the American Hockey League for a few starts before he returned to the NHL, but Providence had multiple games canceled because of COVID-19.
In four starts with Boston, he is 2-2-0 with a 4.28 goals-against average and .844 save percentage. Rask will be 35 on March 10.
"He's not where he needs to be," Bruins coach Bruce Cassidy said. "I think that's evident, and we weren't sure he would be this soon either."
The Bruins (24-13-2) begin a three-game road trip Wednesday at the Colorado Avalanche (10 p.m. ET; TNT, SN, TVAS). Cassidy confirmed that goalie Linus Ullmark would start, and then a decision would be made whether Rask would start Friday at the Arizona Coyotes or Sunday at the Dallas Stars.
"He'll need more starts, and then we have to evaluate it, right?" Cassidy said. "Right now, (he's) not where he needs to be. … He's got to sort through it, get through the kinks in his games, track pucks a little better, find pucks, puck touches, all the things that you have to get back into your game where he feels good about it."