Case Keenum took over the final drive of the first half Monday night and began the second half under center with the Vikings leading the Chicago Bears, 3-2, at Soldier Field. The Vikings went on to win the game 20-17.
Zimmer told reporters after the game Bradford "aggravated" his knee during the first half. Bradford, who missed three games because of a knee injury heading into Monday, stayed in uniform on the sideline during the second half.
"He aggravated his injury when he got tackled on one of the plays," said Zimmer, who described Bradford as day to day. "I just thought it was best for him that we got him out of there. He didn't want to come out. He wanted to stay in there and fight. I didn't want to get him injured anymore.
Zimmer said he didn't believe the Vikings made a bad decision by starting Bradford.
"We wouldn't put him on the field if he wasn't healthy enough to play. He was very confident about it. He felt good about it. The medical people felt good about it, everybody. ... I don't think there was any doubt that he was ready to go."
Bradford struggled in his return after missing the past three games with a knee injury. The veteran looked rusty from the get-go. He missed his first three targets, tossing balls high, low and wide. Bradford also made head-scratching decisions, including holding the ball in his own end zone for-ev-er and taking a safety. He finished the first quarter 1-of-5 passing for minus 5 yards and the safety.
More than anything Zimmer needed to take Bradford out for his own safety. The quarterback couldn't move in the pocket. Unable to flee any hint of pressure, Bradford was a sitting duck, taking four sacks. Bradford looked scared to drive the ball with his injured lower leg, which led to limp tosses.
Bradford ended the half 5-of-11 passing for 36 yards. The Vikings' offense totaled 34 yards on 26 plays with Bradford under center.
Keenum has been solid under center for Minnesota. With the Vikings' defense bottling up Mitchell Trubisky and the Bears' offense, Zimmer couldn't chance blowing a winnable road game by sticking with Bradford. Keenum gave Minnesota a better chance to win.