(AP Photo/Darron Cummings)Sam Bradford's return to the Vikings' starting quarterback job didn't last long.

The Vikings pulled Bradford in the second quarter on Monday night, replacing him with Case Keenum after Bradford started 5 of 11 for 36 yards. The quarterback, who'd missed the Vikings' last three games with left knee issues, was sacked four times, including once for a safety, and appeared unable to move in the pocket.

Bradford was limited during all three of the Vikings' practices this week, just as he was before the Vikings' second game against the Pittsburgh Steelers, when the team decided not to play Bradford after a pregame workout. The day after that game, while explaining his surly postgame press conference in Pittsburgh, coach Mike Zimmer said, "Where I get frustrated, is I want to protect my players. I'm never going to put a player out on field that cannot take care of themselves."

The Vikings have a 3-2 lead over the Bears at halftime.