Rask was 26-8-6 last season with an NHL-leading 2.12 goals-against average (minimum 20 games) and .929 save percentage, which was second under the same parameters, and was a finalist for the Vezina Trophy voted as the best goalie in the NHL.
He entered the Toronto bubble for the Stanley Cup Playoffs with the Bruins, who won the Presidents' Trophy with the best record in the regular season, but decided to opt out less than two hours before Game 3 of the Eastern Conference First Round against the Carolina Hurricanes.
"I got a phone call the night before that our daughter wasn't doing so well at that point," Rask said. "They had to call an ambulance and everything. So obviously at that point my mind's spinning. I'm like, I need to get out of here."
He informed Sweeney the next morning and returned to Boston, where he remained through the offseason. Boston defeated Carolina before losing in five games to the Tampa Bay Lightning in the second round.
"Obviously, it was a tough decision to leave, but then again, it wasn't, because I knew that it was more important for me to be at home at that time," Rask said. "So that was easy to live with."
Rask said he spoke with Jaroslav Halak, who replaced him as the starter, and other teammates, who reassured him and gave him their support, but he did find it tough to watch the rest of the games in the playoffs knowing that "you could be there, you should be there, playing hockey."
After Rask left the bubble, there were reports that the Bruins could be exploring trade options for the goalie. Asked if he ever felt that his future in Boston was uncertain, Rask said only, "Nope."
This season, Bruins coach Bruce Cassidy said Rask and Halak are expected to split the goaltending duties again as they did the previous two seasons, when Rask made about 55 percent of the starts.
Boston, which will play in the MassMutual East Division, opens its season at the New Jersey Devils on Jan. 14.
"The good news is there's not a lot of travel, so that can help a goaltender recover," Cassidy said Tuesday. "So that might edge his games up. So that's our original plan. We're not going to deviate too much from that number, percentagewise, whether it's 56 (games) or 82.
"We could get into the middle of March, not be where we want to be, and need more starts from one of the two goalies. We'll adjust accordingly but that's the original plan."
Rask has played his entire NHL career for the Bruins since being acquired in a trade with the Toronto Maple Leafs on June 24, 2006. He is Boston's leader in games played among goalies (536), wins (291) and save percentage (.922), and second in GAA (2.26; Tiny Thompson is first at 1.99).
Rask won the Stanley Cup with the Bruins in 2011, when he was the backup to Tim Thomas, and since becoming the starter in 2012-13, he has helped them reach the Cup Final twice (2013, 2019).