Gagne had over six minutes of ice time over 11 shifts and three shots on goal in Los Angeles' 4-0 victory that gave the Kings a commanding 3-0 series lead.
Gagne, a former two-time 40-goal scorer, had been sidelined since suffering a concussion against the Phoenix Coyotes the day after Christmas. He had seven goals and 10 assists in 34 games, but had not scored since Nov. 17.
Gagne is believed to have suffered three concussions in five months as a member of the Philadelphia Flyers during the 2007-08 season. While playing with the Tampa Bay Lightning last season, he also missed parts of the playoffs with another head injury.
The move would be surprising, considering the Kings have won 14 of 16 playoff games and no players appeared to have suffered significant injuries in the first two games of the finals with the Kings leading 2-0 and back-to-back overtime victories.
Sutter said before the playoffs that he wasn't even sure if Gagne was in North America and that he would be unavailable to play in the postseason. But the 32-year-old from Quebec resumed practicing as the Kings got deeper into the playoffs.
If there's one area Gagne could contribute, it's on the power play. The Kings are 6 for 77 with the man-advantage in the postseason. Gagne has scored 90 power-play goals in his 12-year-career.
Dan Arritt covers hockey for ESPNLosAngeles.com.