By Matt Zahn

CHICAGO (CBS)–  CBS 2’s Matt Zahn has the three keys to the game as the Bears face the Denver Broncos.

1. Bears Offense

While the Bears “were just simply awful” in the opener, according to CBS 2’s Matt Zahn, Matt Nagy deserves some of the blame and so does quarterback Mitch Trubisky.

The big question, will Trubisky be any better this week? Zahn said he thinks so.

Zahn explained Trubisky’s offensive line was really bad in week one. Even against what should be a pretty good Denver defense, they simply have to better.

All off-season, Zahn says he has been on the “Trubisky is a pretty good quarterback train” with a chance to take a step forward in his second year in Nagy’s offense. There’s just no reason why he should take a step back, which is what he did in the opener, looking very tentative.

Zahn said he’s looking for Trubisky to use his feet more, either designed runs or more roll-outs

2. Running Game Must Improve

Zahn says this is a no-brainer, the Bears have to run the ball more.

Runningback David Montgomery looked fantastic in Bourbonnais, according to Zahn. In the limited time we saw him against Green Bay, the Bears only ran the ball three times in the second half. Look for the Bears rookie to get more action against Denver

Along those same lines, Zahn said he looks for more runningback Tarik Cohen, also working runningback Mike Davis into the mix as well.

3. Altitude Issues

Finally, watch for Bears players going for oxygen on the sideline.

Sometimes Zahn thinks altitude is an overplayed factor in games in Denver, but not when it comes to early season games. Perhaps because teams are still working themselves into their top condition.

In their first two home games of the season, the Broncos are 21-1 since 2001. The Bears did practice and play a preseason game in Denver last year, which might help them.

While this game is not a must-win for the Bears, the following four games they play are against the Vikings, Saints, Rams and Eagles. That first place schedule is a big beast, so Zahn says the time to panic may be coming sooner rather than later.