WHAT TO WATCH 4
Key matchup
Quarterback Colin Kaepernick might be the 49ers’ most dangerous running threat, but defenses can’t sleep on running back Carlos Hyde.
Hyde, who rushed for 103 yards and two touchdowns against the Seahawks in Week 3, is picking up steam after missing two weeks with a shoulder injury. He had 86 yards on 19 carries on Nov. 20 against the Patriots and 65 yards on 13 carries last Sunday against the Dolphins.
Linebackers Jerrell Freeman and Danny Trevathan have been stout against the run for most of the season. With both of them out — Freeman because of a suspension and Trevathan because of a knee injury — that chore falls to rookie Nick Kwiatkoski and second- year man John Timu.
‘‘ He’s a hard runner, there’s no question about that,’’ Kwiatkoski said of Hyde. ‘‘ If he gets downhill, he can do a lot of things. Anytime there’s a back like that, you have to be ready to tackle and just have to know where he’s at on the field at all times.’’
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The Bears will be without most of their most dangerous weapons ( Jay Cutler, Alshon Jeffery, Kevin White and Zach Miller), but they still should have bigplay possibilities against the 49ers, who have allowed 54 plays of 20 or more yards — the most in the NFL.
The Bears had four plays of 20 or more yards with Matt Barkley at quarterback last week against the Titans, but the longest were 23- yard passes to running back Jordan Howard and receiver Marquess Wilson.
Player to watch
Timu will be making his second start of the season, but the last time he started — in a 17- 14 victory against the Lions in Week 4 — he had the veteran Freeman next to him. This time, it’ll be the rookie Kwiatkoski.
Timu, an undrafted free agent from Washington, started three games last season. He’s much more comfortable coming in this time with that experience.
‘‘ I think experience helps you see things a little more clearly and play a little faster,’’ Timu said. ‘‘ There’s no holding back as far as being slower to make a play. Just take my keys, tendencies I’ve got and tip sheets from the coaches and roll with it. Know what you know and play what you see.’’
X- factors
Winter weather might make its first appearance of the season Sunday at Soldier Field, with a possible rain/ snow mix and temperatures in the 30s.
The 49ers, coming off a loss to the Dolphins, practiced at the University of Central Florida in Orlando, where temperatures were in the 80s for most of the week. The Bears practiced in Lake Forest ( though they were indoors Friday), but conditions might be worse Sunday.