Stamkos scored on a breakaway on his team's first shot as part of a two-goal effort as Tampa Bay defeated Vancouver 4-2 to hand the Canucks their first loss of the season.
Lack, who called Stamkos one the three best players in the world at Saturday's morning skate, could only watch as Tampa Bay's captain slipped a backhand past him just 53 seconds into the game.
"I kind of felt like I had him and then it kind of just snuck through," Lack said after finishing with 20 stops. "He's a great player — probably not the player you want to give a breakaway to at the start, but it was a good goal."
The Canucks actually had sustained pressure in the Tampa Bay zone prior to the goal, but a turnover by Vancouver captain Henrik Sedin led to Stamkos' opener.
"It's funny how the great ones find a way to get into open ice and pucks seem to find their sticks," said Lightning head coach Jon Cooper. "That was pivotal for us because it's early in the game, we're kind of playing in the (defensive) zone and we get the big break and he scores. That took a little air out of Vancouver's tires and set the tone for us."
Added Sedin: "We had a great shift. We felt good. We had a few chances there and (I) tried to make a play. Just one of those plays that maybe you shouldn't do against a really good player, but I made it and it cost us a big goal."
Ryan Callahan also scored and added an assist for Tampa Bay (3-1-1), while Ben Bishop finished with 30 saves to kick off a five-game road trip with a win.
Lack was making his first start of the season in place of Ryan Miller, but Canucks head coach Willie Desjardins had no problem with his performance.
"Stamkos right off the start on a breakaway is a tough way to start," said Desjardins. "He's got a great attitude and I have no worry about Eddie Lack. He's a real good goaltender and I've got lots of confidence in him."
Alex Killhorn had the other goal for the Lightning, while Ondrej Palat chipped in with two assists.
Tampa Bay lost standout defenceman Victor Hedman midway through the second period to an upper-body injury and Cooper said he will be sent home to be re-evaluated.
"That's a big loss, he's playing so well and he's a horse for us," said Stamkos, who broke his leg last season. "That just shows the character on this team. We've dealt with injuries and adversity before and come out on top."
Alexander Edler, with a goal and an assist, and Chris Higgins scored for Vancouver (3-1-0), which opened with two wins against the Edmonton Oilers — including Friday night's road victory — and one over the Calgary Flames, but found it much tougher sledding against one of the Eastern Conference's best teams.
Down 2-1 after 20 minutes, the Canucks evened the score at 2:42 of the second when Edler took a pass from Daniel Sedin off the rush on a power play and ripped a shot past Bishop for his first of the season.
After Vancouver failed to score on three straight man-advantage opportunities later in the period, the Lightning retook the lead at 16:48 just after a 5-on-3 power play expired. Stamkos shattered his stick on a one-timer, went to the bench to pick up some new lumber and promptly fed Callahan, who ripped his third past a helpless Lack after some prolonged pressure.
Desjardins wasn't impressed with his team's discipline, with Alexandre Burrows taking a roughing penalty before Kevin Bieksa went off for a trip to give the Lightning their two-man advantage.
"We've got to be smarter. They've got a real good power play. We know that. It's not that that surprised us," said Desjardins. "It comes down to how bad do you want to win? Do you want to win bad enough that you'll have the discipline to stay out of the box. It cost us a little bit tonight. We've got to be better."
Tampa Bay stretched its lead to 4-2 at 6:04 of the third when Lack made a great save off Tyler Johnson in front only to have Killhorn shovel home the rebound for his second of the year.
The Canucks announced in an email to season ticket holders on Friday that the game against the Lightning would not be a sellout, snapping a streak of 474 straight full houses at Rogers Arena. The last time Vancouver played before a less-than-capacity crowd at home prior to Saturday was on Nov. 12, 2002.
After Stamkos gave Tampa Bay the early lead, the Canucks — who were looking to open with four consecutive wins for the first time since 1992 — got things back to even when Higgins followed up his own rebound for his first of the campaign at 7:15.
But Stamkos grabbed his second of the night and fifth of the young season just 1:11 later. Canucks defenceman Dan Hamhuis fanned on a clearing attempt behind his net and Callahan poked the puck out front to Stamkos, who scored to give Tampa Bay a 2-1 lead on just three shots.
"I thought we gave this game away. We showed on a back-to-back night we can play the best teams," said Henrik Sedin. "I thought we could have won the game. I cost us the first goal and then we gave them the second goal as well.
"We pushed hard to come back in the game but then we gave them a 5-on-3 and that's where I think the momentum changed."
Notes: The Canucks start a three-game road trip on Tuesday against the Dallas Stars. ... The Lightning continue their road trip on Monday against the Oilers. ... The Canucks visit the Lightning in their only other meeting on Jan. 20. ... Vancouver defenceman Ryan Stanton sat out after suffering an injury in Friday's game, with Yannick Weber taking his spot in the lineup... Frank Corrado was recalled from the AHL's Utica Comets but didn't dress. ... Among the 18,647 in attendance was actor John Travolta. Capacity at Rogers Arena is 18,870.