The 30-year-old Gill is replacing defenseman Nick Grossmann, who injured his right knee in the Flyers' 2-1 home win on Friday in Game 4. The series is tied 2-2.
Gill played in only six games during the regular season, but he has been in 110 career playoff games in 16 NHL seasons.
The Rangers are also making a change in their Sunday lineup, inserting 21-year-old forward J.T. Miller in place of veteran agitator Daniel Carcillo, who is a healthy scratch.
Carcillo played in the previous two games after sitting out the first two. Miller, who had three goals and three assists in 30 games this season, is making his postseason debut.