Gionta played in Montreal's 4-1 victory over the Edmonton Oilers on Thursday night.
He had rejoined his teammates in Calgary for their game against the Flames on Tuesday after attending to a "family emergency."
"We don't know when he's going to come back," said Canadiens head coach Michel Therrien after his team's practice at Rogers Arena on Friday. "He's an important part of our team. He's a good leader, but right now I don't know when he's going to come back."
The 34-year-old Gionta has one goal and one assist in four games with Montreal so far this season.
Following Saturday's game in Vancouver, the Canadiens wrap up their four-game road trip with a stop in Winnipeg to face the Jets on Tuesday.