Depth is the issue here for the Broncos.

Their top two tight ends, free-agent pickups Joel Dreessen and Jacob Tamme, are securely on the roster and will likely be used extensively and frequently targeted by Peyton Manning. Tamme was the target on Manning's first two throws on Thursday night, but Dreessen looks to be a potent goal-to-go threat, given that his blocking ability can keep foes off balance.

This is the polar opposite of last year, when Broncos tight ends collectively averaged a meager 1.4 receptions and 19.4 yards per game after Tim Tebow became the starting quarterback.

For the entire season, the Broncos got just 40 receptions out of their tight ends. This year, they might surpass that tally by Halloween.

But if something happens to Tamme or Dreessen, questions abound. Beyond them, the drop-off is steep -- especially with second-year veteran Virgil Green suspended for the first three games of the year for taking an ADHD medication with a banned substance.

Fellow 2011 draft pick Julius Thomas remains an intriguing, athletic prospect after spending most of his Portland State years as a basketball player, but he didn't play Thursday and has been limited through most of training camp because of the lingering effects of ankle surgery he underwent in March.

That could give Cornelius Ingram an opening. Since entering the NFL in 2009, he's been on three practice squads and spent a year on injured reserve. But the Broncos' need for depth could give Ingram a shot; he responded in the preseason opener with two catches for a team-leading 45 yards and a 25-yard touchdown.

Undrafted rookie Anthony Miller also played at Chicago on Thursday, but wasn't targeted. Denver likely needs two backups given how often they plan to use Dreessen and Tamme.

The lingering questions revolve around whether Thomas recovers and Ingram develops enough for the Broncos to entrust their depth to them until Green returns. If not, the team might look for seasoned potential backups on the open market, as they did at safety (Jim Leonhard) and linebacker (Keith Brooking).

Projected tight ends: Tamme, Dreessen, Thomas, Green.

For up-to-the-minute Broncos updates, follow Andrew Mason on Twitter at @CBSSportsNFLDEN and @MaxBroncos.