The Stars outshot the Canucks 5-2 in overtime, with Lack making several saves to keep the game tied, including denying Cody Eakin in the crease.
Kari Lehtonen made 24 saves for the Stars. They had won four in a row.
Dallas remained eight points behind Winnipeg for the final wild-card spot in the Western Conference, with just seven games left.
CALGARY, Alberta -- Ales Hemsky scored twice in regulation, Tyler Seguin had the only goal in the shootout, and the Dallas Stars beat the Calgary Flames 4-3 Wednesday night for their seventh win in eight games.
Jamie Benn also scored for Dallas, which pulled six points behind Winnipeg for the second wild-card spot in the Western Conference.
Dereky Engelland got his first two goals of the season, and Gaudreau also scored in regulation for Calgary. The Flames remained third in the Pacific Division, one point up on Los Angeles -- which is outside of a playoff spot.
The Stars won for the sixth time in seven games.
The Sabres, last in the NHL with 47 points, are 1-8-2 in their past 11 games.
DALLAS -- Kari Lehtonen stopped all 33 shots, including a penalty shot, for his fifth shutout this season and 32nd of his career, and the Dallas Stars defeated the Chicago Blackhawks 4-0 on Saturday night.
The Blackhawks had been 6-0-1 in their previous seven games.
Benn set up Ritchie's deflection goal at 2:15 of the second, and put his own rebound past Marc-Andre Fleury at 3:37 for a 2-0 lead.
Kris Letang scored the Penguins' second power-play goal in nine games at 13:26 of the second. They have scored only twice in losing their last four games.
Dallas' Kari Lehtonen made 15 of his 31 saves in the third period to preserve his 30th win of the season. Fleury had 24 saves.
The Stars won for the sixth time in their last eight games to keep their slim playoff hopes alive. With 11 games remaining, they are eight points away from the Western Conference's final wild-card spot.
DALLAS -- Jake Allen made 28 saves for his fourth shutout this season, and Vladimir Tarasenko broke a scoreless game with a goal in the third period in the St. Louis Blues' 3-0 win over the Dallas Stars on Sunday.
Tarasenko skated down the slot and fired a shot past Kari Lehtonen into the lower right corner 3:33 into the third. It was Tarasenko's second game-winning goal in Dallas this season.
Steen and Oshie each had a goal and an assist, and teammate Alex Pietrangelo had two assists. St. Louis killed all six Stars power plays. The Blues' penalty killers have been successful in 29 of 30 chances over the last nine games.