INDIANAPOLIS -- Michael Pittman Jr., the Colts' No. 1 wide receiver, has suffered a back injury that is expected to sideline him for multiple games, sources told ESPN's Adam Schefter on Wednesday. Pittman played the entirety of last Sunday's loss at the Jacksonville Jaguars but is believed to have been injured in the game. He joins a long list of key Colts  players dealing with injuries, leaving them looking for answers at numerous positions. The Colts have not yet determined whether Pittman will be placed on injured reserve, which would sideline him for at least four games. Pittman has 22 receptions for 238 yards and a touchdown through five games this season and has 3,159 combined receiving yards in the past three seasons. He was rewarded during the offseason with a three-year, $70 million contract extension in March that prevented him from reaching free agency. Also Wednesday, the Colts revealed that starting receiver  Josh Downs is dealing...