Case Keenum came off the bench to energize the offence and Kai Forbath kicked the game-winning field goal with 12 seconds left as the Minnesota Vikings edged the Chicago Bears 20-17 on Monday.

Keenum replaced starting quarterback Sam Bradford who struggled mightily in his return to the lineup after missing the last three games with a knee injury. Bradford completed just five of 16 passes for 36 yards.

Keenum, who had been starting in place of Bradford, made 17 of 21 passes for 140 yards and a touchdown for the Vikings, who improved to 3-2 with their first road win this season. 

Forbath booted a 26-yard field goal with 12 seconds remaining to lift the Vikings to victory.

The Bears' quarterback woes continued as rookie Mitchell Trubisky tried but failed to rally the troops in his first NFL start. Trubisky was given the start after Chicago (1-4) dumped veteran Mike Glennon because of his eight turnovers in the last three games.

Glennon was signed to a hefty contract and was supposed to last the whole season. But the Bears urgency for results left them with task of trying to win Monday with an unproven rookie. It marked the first time Chicago started a rookie quarterback since Kyle Orton in 2005. 

Trubisky completed 12 of 25 passes for 119 yards and a touchdown. But he tossed an interception to Vikings safety Harrison Smith deep in Bears territory to set up the go-ahead score.

Chicago dropped its second consecutive game.

Keenum rebooted the Vikings' offence. He opened the second half with a 13-play, 75-yard drive that culminated in a 13-yard touchdown pass to tight end Kyle Rudolph. The play extended the Vikings' lead to 10-2.

Running back Jerick McKinnon earned 95 yards and a touchdown on 16 carries.

Chicago's Jordan Howard gained 76 yards on 19 carries.

The Vikings next game is Sunday when they host the Green Bay Packers.