Three things: 49ers-Broncos

Three things to watch for Sunday night in the San Francisco 49ers' third exhibition game, this one at Denver (4 p.m. ET):

1. Starting QBs. The 49ers have Alex Smith. The Broncos have Peyton Manning. The 49ers have gone out of their way to frame their offseason interest in Manning as nothing more than routine investigative work on an available free agent. The excitement over Manning's arrival in Denver has been intense enough to obscure significant questions about his physical prospects following four neck surgeries. I'm interested in seeing how well Manning throw the ball downfield, and how well Smith plays by comparison. Can Manning still sling the deeper passes with authority? And can the 49ers' pass-rush, a bit muted at times this preseason, get to him?

2. Two-way threat. Demarcus Dobbs has impressed the 49ers on both sides of the ball. He figures to get playing time as a pass-rusher on defense, particularly with Aldon Smith limited by injury (and possibly not available for this game). The 6-foot-6, 275-pound Dobbs also has a chance to emerge from this preseason as the third tight end behind Vernon Davis and Delanie Walker. Any work he gets at the position will be worth monitoring as well. Coach Jim Harbaugh has sounded enthusiastic regarding Dobbs' prospects as a two-way threat. Dobbs, 24, did play both defensive end and tight end in high school, but he was a defensive player at the University of Georgia.

3. Perrish's push. The lead-in should sound familiar. It's a repeat from last week. The note should be a lot more relevant this time. Cornerback Perrish Cox, who missed the 49ers' most recent game, is expected to play in this one. He's been a welcome addition to the 49ers' secondary this offseason, pushing Chris Culliver for a spot in the 49ers' nickel defense. Cox last played in a regular-season game as a rookie with Denver in 2010. If getting a chance to face his former team weren't enough, Cox also gets a shot at Manning. That's enough to get any defensive back's attention.