The Denver Broncos come into the preseason with Super Bowl aspirations, but some real questions about their offensive line and defense. Meanwhile the San Francisco 49ers came close to the Lombardi Trophy, but now are missing a critical piece of their offense.

Here are three things to watch when the teams meet tonight at 9pm EST.

1) After losing center Dan Koppen to a torn ACL, how will the offensive line fare? They struggled at times last season and it is awfully tough to overcome an injury at one of your key anchors on the line. The team went and improved the offense, adding Wes Welker and rookie running back Montee Ball, but if they can't find the fix in the middle—be that Ryan Lijia, Manny Ramirez or someone else—the season could end badly.

2) The 49ers have issues of their own due to injury. When Michael Crabtree tore his Achilles tendon during OTAs, it was certainly a blow to this offense. Anquan Boldin went from being a nice No. 2 to being a necessary No. 1. Who's going to take over the No. 2 though? A.J. Jenkins, Ricardo Lockette and Quinton Patton have been battling it out and tonight will be a chance to create some separation.

3) Both secondaries have question marks. The Broncos added Dominique Rodgers-Cromartie to help out Chris Harris and Champ Bailey, but whether that will be enough is still a question, especially if losing Elvis Dumervil hurts the pass rush more than they think it will. Meanwhile, the 49ers replaced safety Dashon Goldson with rookie Eric Reid and hope Nnamdi Asomugha can recover some of the form he lost during his stint with the Philadelphia Eagles.

Andrew Garda is a member of the Pro Football Writers Association. He is also a member of the fantasy football staff at Footballguys.com and an NFL writer at Bleacher Report. You can follow him at @andrew_garda on Twitter.