The defenseman was elbowed in the head by Dallas Stars forward Corey Perry 2:44 into the first period of the Stars' 4-2 victory in the 2020 Bridgestone NHL Winter Classic at Cotton Bowl Stadium on Wednesday.
Perry received a five-minute major for elbowing and a game misconduct. He was suspended for five games following a hearing with the NHL Department of Player Safety on Friday.
There is no timetable for Ellis' return, but the earliest he would be able to come back from injured reserve is Jan. 9, when Nashville plays at the Chicago Blackhawks.
Ellis has 28 points (six goals, 22 assists) in 39 games this season and 242 points (68 goals, 174 assists) in 517 games in nine NHL seasons, all with the Predators.