The Bears defense performed well on third down in Sunday's 23-20 overtime loss in Minnesota, allowing the Vikings to convert just 4-of-17 opportunities (24 percent).
Fourth downs were a different story, however. The Vikings were successful on all three of their fourth-down plays, sustaining second-half drives that resulted in two field goals and a touchdown.
Peterson's 19-yard run on fourth-and-one from the Chicago 31 led to Matt Cassel's 8-yard touchdown pass to Greg Jennings, closing the gap to 20-17 with 7:41 left in the fourth quarter.
The costliest conversion the Bears allowed came with just under two minutes to play in regulation when the Vikings, trailing 20-17, faced fourth-and-11 from the Chicago 8.
Unloading an instant before blitzing linebacker James Anderson arrived, Cassel completed a 20-yard pass to Jerome Simpson over the middle. The play sustained a drive that eventually led to Walsh's 30-yard field goal with :20 remaining, which forced overtime.
"[Cassel] made an incredible play," said coach Marc Trestman. "James was running right at him. He threw it around James. He could not have seen the throw, could not have seen the receiver, and the receiver ran right through the ball on the hash mark and made the play.
"It was a very good play by [Cassel]. They were in a quick snap and they got it off and we were just a hair late getting to the quarterback. [Anderson] went to the quarterback untouched."
Sunday marked the first time a Bears opponent converted as many as three fourth-down plays since the Vikings went 3-of-4 on Oct. 19, 2008 in a 48-41 Chicago win at Soldier Field.
Super sub: Starting in place of the injured Major Wright at strong safety Sunday in Minnesota, veteran Craig Steltz tied for the Bears' lead with 12 tackles.
It was Steltz's eighth start in six seasons with the Bears and his first since the 2011 season finale, which was also against the Vikings in the Metrodome.
"I felt we got a heck of a performance out of Craig," Trestman said. "He was at the line of scrimmage. He played in the box well. He wasn't perfect-none of us were-but he really played well and had a good performance."
Nothing doing: After Walsh's game-tying field goal late in the fourth quarter, the Bears took over at the 50 with :14 left in regulation following Devin Hester's 57-yard kickoff return.
But they were able to muster only two yards on two plays as Josh McCown was sacked at the line of scrimmage before completing a 2-yard check-down pass to Earl Bennett.
"We just didn't get it done," Trestman said. "I hold myself accountable. I think we could have done a better job there of getting it done. We didn't do it."
Having advanced only to the Minnesota 48, Robbie Gould attempted a desperation 66-yard field goal that was well short as time expired in the fourth quarter.
Roster move: The Bears on Tuesday re-signed defensive tackle Tracy Robertson to the practice squad. He made his NFL debut Nov. 24 in the Bears' loss in St. Louis but was waived last week when safety Sean Cattouse was promoted from the practice squad to the active roster.
Robertson entered the NFL in 2012 as an undrafted free agent with the Texans. He also spent time with the Lions, Patriots and Dolphins without appearing in a regular-season game.