Killorn has missed three games with an undisclosed injury. He blocked a shot by Canadiens defenseman Jeff Petry with his left leg with 6:28 remaining in the second period of a 5-1 win in Game 1, and after playing three more shifts left the game 56 seconds into the third period.
The Lightning can sweep the best-of-7 series and win the Stanley Cup on Monday.
Mathieu Joseph has taken Killorn's spot the past three games. He had an assist, was plus-2 and had five hits playing on the fourth line with Tyler Johnson and Patrick Maroon in a 6-3 win in Game 3 on Friday.
"Mathieu Joseph comes in and has a huge impact," Maroon said. "Those two games he plays, it's that brotherhood bond we have, the compete and the next man up mentality."
Killorn had been playing regularly on the second line with Anthony Cirelli and Steven Stamkos and on the top power-play unit with Stamkos, Nikita Kucherov, Brayden Point and defenseman Victor Hedman. He's also part of the penalty kill.
Johnson played in Killorn's spot as the left wing on the second line in Game 2 but moved back to center the fourth line in Game 3, when Colton was the left wing with Cirelli and Stamkos.
Killorn has scored 17 points (eight goals, nine assists) in 19 playoff games. He is tied for second in goals on Tampa Bay with Stamkos and Kucherov, behind Point, who has scored 14.
The Lightning were trying to win the Stanley Cup for a second straight season. They defeated the Dallas Stars in six games in the Final last season and would be the first team since the Pittsburgh Penguins (2016, 2017) to repeat as Stanley Cup champions.
