Tom Brady will be without one of his favorite targets Sunday when the New England Patriots face the Chicago Bears at Soldier Field.

Four-time All-Pro tight end Rob Gronkowski did not travel with the Patriots to Chicago because of a back injury, according to the Boston Globe. The Patriots tweeted Sunday morning that he has been ruled “out” for the game.

Gronkowski, 29, had played in every game this season for the Patriots, who are 4-2 and tied for first place with the Dolphins in the AFC East. The 6-foot-6, 268-pound veteran has a team-high 405 yards and a touchdown on 26 catches this season, his ninth.

Patriots starting right tackle Marcus Cannon was ruled out Friday because of a concussion suffered last week against the Chiefs. LaAdrian Waddle likely will start in his place, according to the Boston Herald.

For the Bears, outside linebacker Khalil Mack, who suffered a sprained right ankle Sunday against the Dolphins, is questionable. Mack, who has five sacks, four forced fumbles and an interception return for a touchdown, never has missed a game during his five NFL seasons, a streak of 69. He had limited participation in practice Friday.