Boston's ace netminder has missed 17 of the club's last 18 games and for the season has suited up just 15 times with an 8-4-0 record. Given his lack of reps, Cassidy expects Rask to make up for lost ground over the final month of the season despite the heavy schedule facing the Bruins.
"That's a later decision," said Cassidy. "Obviously with only so many games left - Tuukka's been out a while now - it's not a switch. I don't care what position you play, you need reps. Very few guys can just jump back in there after missing time. I think Tuukka's going to need his share.
"As far as the rest part, obviously that depends on his play, how does he feel? Where is he at physically? But how is his timing most importantly? Those are some things we'll have to look at as we go along, so it's hard for me to answer now."
Ultimately, Cassidy explained, his goaltending decisions will be based on merit and which backstop gives the team the best chance to succeed as they look to secure a playoff spot. The return of Jaroslav Halak, who has been on the COVID protocol list for nearly two weeks, will soon provide Boston's bench boss plenty of reliable options in goal with the emergence of young netminders Jeremy Swayman and Daniel Vladar in recent weeks.
"Obviously, knowing that Swayman and Vladdy have been good for us, given us a chance to win," said Cassidy. "And then there's Jaro. He's been off for a while now, too, so where is his timing going to be? So, it's going to be tough to get them all their reps and starts with how many games we have left. And then it's a matter of, we're still in a playoff fight here, so we have to play the guy that gives us the best chance to win.
"But the most important one for us right now is what's in front of us and that's Tuukka's next start which looks like it's going to be [on Thursday night], and hopefully play well in front of him and he gets back in a rhythm."
Cassidy did acknowledge that Swayman could see some starts down the stretch given how well he has played over his first four appearances. The 22-year-old is 3-1-0 with a .926 save percentage and 2.22 goals against average.
"Yeah…he certainly looks composed, has been composed," said Cassidy. "I don't have a crystal ball either. I don't know what's going to happen in three weeks. I don't know how Jaro is going to recover once he's off the COVID list. How's Tuukka's time off going to treat him? Is it going to treat him well, where the time has done him good, and he finds his game quickly, or is it going to take a while?
"There's a lot of questions that go into it, but we haven't ruled him out being a guy that could see some extra starts that we didn't anticipate. That's just performance related."