Lack looks to help Vancouver stay hot after a six-day break as it visits the slumping Calgary Flames on Sunday night.
The Canucks (22-11-6) improved to 9-1-1 over their last 11 with a 2-1 victory over Winnipeg last Sunday, but Luongo exited toward the end of the first period with a lower-body injury.
Lack entered and stopped 15 of 16 shots to earn the victory. Though Luongo went into that contest 5-1-1 with a 1.75 goals-against average over his previous seven starts, Lack appears ready to carry the load for as long as Luongo is out.
"I'm just trying to take it day by day and just improve my game," Lack said. "Once I get in there, I'm focused and just trying to do my best to help the team. It's been good so far."
The rookie is 6-2-0 with a 1.93 GAA in seven starts and four relief appearances. He's 4-0-0 with a .955 save percentage this month.
"This is what happens when you have an injury, and we have total confidence in his play," Tortorella said. "I'm not sure what's going to happen with Roberto. Lack plays (Sunday) and we go from there."
Lack will be returning to the site of his first career start. He made 32 saves before Mike Santorelli scored his second goal of the game in overtime to help the Canucks beat the Flames 5-4 on Oct. 6.
"I'm just looking at Calgary," Lack said. "I've played once there before so I know the building and everything. I'm just going to try and get two points out of there."
Tortorella said Luongo is considered day to day, though he didn't offer any updates on Alex Burrows (jaw) or Alex Edler (knee). Burrows has been out since Dec. 1, while Edler hasn't played since Dec. 3.
"You can't depend on just a couple of guys," Tortorella said. "I don't think this team for the last little while has. I think everybody has kind of chipped in."
Vancouver has won three straight meetings with the Flames (14-18-6), who are 1-3-2 over their last six after falling 2-0 to Edmonton on Friday.
Calgary has split the first two on its five-game homestand.
"The bottom line is we didn't play a very good game," coach Bob Hartley said. "We didn't give ourselves a chance to win. Here's one game that I didn't think we had our usual jump."
The Flames were shut out for the second time in their last five games after not being blanked at all through their first 33.
"We didn't get the bounces, but we weren't good enough," said defenseman Mark Giordano, who had a shot ring off the post. "We have to generate more and find ways to score. We were standing around and not moving our feet enough."
Reto Berra stopped 26 of 27 shots, but again didn't receive much offensive support. He's 2-3-0 over his last five starts despite a 1.79 GAA.
Berra has started the last two, but Karri Ramo could get the nod against the Canucks. Ramo is 0-1-2 with a 3.26 GAA over his last three outings.
Flames 19-year-old rookie Sean Monahan, who has no points in his last five but is tied for fourth on the team with 16, scored in the first meeting with Vancouver.