Earlier Tuesday, the Kings said Gagne did not accompany the team to Chicago on Tuesday morning after suffering an upper-body injury the night before during a 4-3 victory against the visiting Phoenix Coyotes.
The injury appeared to occur late in the first period after he was checked into the glass. He returned to play six shifts in the second, then left the game. Kings coach Darryl Sutter said afterward that Gagne was "banged up" but didn't elaborate.
Sutter is expected to provide an additional update after the morning skate Wednesday, prior to the team's game that night against the Blackhawks. Gagne has not been placed on injured reserve, but the Kings currently have 24 players on their roster and must get down to 23 by the end of Tuesday.
After scoring seven goals in his first 17 games with the Kings, Gagne has not scored in the last 17. The Kings rank last in the league in scoring and went 14 straight games without scoring more than two goals before the victory against the Coyotes.
Gagne, 31, has experienced a number of injuries in the last five seasons, most notably what's believed to be three concussions in five months during the 2007-08 season. The two-time 40-goal scorer came back the following season and totaled 34 goals and 40 assists in 79 games, but a double hernia sidelined him for 24 games the following year. He was traded to the Lightning in July 2010.
During Game 1 of the Eastern Conference semifinals last April against the Washington Capitals, Gagne was briefly knocked unconscious after he was checked to the ice and hit his head. He sat out the remainder of the series and returned to play in the Eastern Conference finals, scoring three goals in the seven-game loss to the Boston Bruins.
Information from ESPNLosAngeles.com's Dan Arritt was used in this report.