Johnson, 23, got hurt during Chicago’s 5-4 loss at Toronto on Saturday night. He has one goal and three assists in 18 games this season.
Team physician Michael Terry said Johnson will undergo further evaluation on Monday.
The Blackhawks host the Calgary Flames on Monday night.
Connolly has five goals and six assists in 16 games this season with Rockford. The 29-year-old Connolly has 101 goals and 93 assists in 527 career NHL games.
Entwistle has split time between Rockford and Chicago this season. He has two goals and one assist in 12 games with the Blackhawks.