Bears vs. Vikings — What to Watch 4

KEY MATCHUP

Bears quarterback Mitch Trubisky was burned by Vikings safety Harrison Smith in his NFL debut in Week 5. Smith’s fourth-quarter interception in a tie game led to the Vikings’ winning field goal. Now we’ll see how well Trubisky has learned.

After getting snubbed for the Pro Bowl, Smith had two interceptions and eight tackles — including one for loss — to spearhead the Vikings’ 16-0 victory last week against the Packers. It was their first shutout since 1993.

Smith, a starter since he entered the NFL in 2012 and a Pro Bowl player the previous two seasons, is having another fine season. He’s ranked as the No. 1 safety in the NFL by Pro Football Focus.

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The Notre Dame product is one of those instinctive, intelligent defenders who can take advantage of inexperienced players. Four of his five picks this season have come against the Packers’ Brett Hundley (three) and Trubisky.

TRENDING

The Bears’ defense was in a free fall at this time last season, allowing 451, 478 and 374 yards in the final three games to drop from seventh to 15th in total defense.

Even without five Week 1 starters, including outside linebackers Leonard Floyd and Willie Young and safety Quintin Demps, the Bears have reversed that trend season. They’ve allowed 234, 293 and 245 yards in their last three games to jump from 14th to eighth in total defense.

‘‘[Coordinator] Vic [Fangio] wasn’t going to let that happen again,’’ defensive end Akiem Hicks said. “He started talking to us in Week 8. He said: ‘OK, guys, you started to taper off toward the end of last year. We’re not going to have that.’ He harped on us to make sure we’re focused on what we are as a defense. Regardless of whatever else is going on around us, we need to be able to play strong and stout defense like we do.’’

KEY PLAYER

A game against the Vikings’ top-ranked defense neatly bookends Trubisky’s rookie season and serves as a legitimate measuring stick of his progress.

Trubisky was OK in his NFL debut against the Vikings in Week 5 (12-for-25 for 128 yards with one touchdown and one interception for a 60.1 passer rating) at Soldier Field. This one’s one the road, but Trubisky now has 11 games under his belt.

X-FACTOR

The Vikings still have not clinched a first-round bye in the playoffs, so they at least will start with something to play for.

The Bears are playing out the string, but they think they are on the upswing and know this might be coach John Fox’s final game, so they’ll be motivated to finish strong.

Follow me on Twitter @MarkPotash.

Email: mpotash@suntimes.com