Fallout from Dreessen's surgery 

August, 5, 2013
UPDATE: Per Mike Klis of the Denver Post, with the Broncos' depleted TE corps (see below), Julius Thomas "has been getting his first-team chances at the 'F' or 'move' or 'receiving' tight end position throughout the offseason and training camp," while Virgil Green "is a prototype 'Y' tight end, who plays at the line of scrimmage."

Basically, that means that Thomas is more likely to end up catching passes if Joel Dreessen and Jacob Tamme end up out during the regular season, but as I noted below, it's kind of a moot point in fantasy terms.
The setback that Joel Dreessen sustained with his surgically repaired knee will force him to undergo another procedure to repair damage in the joint. It's expected to keep him out for the entire preseason, according to ESPN.com's Jeff Legwold.