There's no escaping the fact that their viability as contenders begins and ends with Manning's right arm.
Manning was an MVP candidate ranked atop Gregg Rosenthal's weekly QB Index entering the 2014 season's midpoint. It was all downhill from there, as Manning's arm -- already the weakest among established NFL starters -- lost what little juice remainedby the season-ending playoff loss to the Indianapolis Colts.
Was the sudden drop-off merely the adverse side effect of a lingering thigh injury? Or is Manning finished as a difference-making quarterback?
Coaches, scouts and executives have spent the past couple of months speculating -- in some cases, the jury is in and handing the judge a rope -- but it's a question with no answer until the bell rings on the 2015 season.
Even if Manning manages to recapture his 2013 form for an entire season, he can't count on reaching those same record-breaking heights.
Welker lost his effectiveness last season. Now Thomas is prepared to defect to the highest bidder next week.
If Elway is resigned to losing his two-time Pro Bowl tight end, the Broncos will have to lean more heavily on new coach Gary Kubiak's stretch-run attack with C.J. Anderson, Ronnie Hillman and Montee Ball, complemented by a defense as stingy as the one that ranked fourth in Football Outsiders' metrics last year.
Unlike most teams switching schemes, the Broncos already have the talent on hand for a smooth transition to Wade Phillips' 3-4 defense.
Von Miller and DeMarcus Ware are natural book-end edge rushers. Brandon Marshall and Danny Trevathan will slide right in at inside linebacker. Derek Wolfe, Sylvester Williams and Malik Jackson comprise the nucleus of a solid defensive line that will need a replacement for soon-to-be-departed nose tackle Terrance Knighton. The secondary remains one of the NFL's best regardless of free agent Rahim Moore's future.
Elway has shown a penchant for pushing his chips to the center of the table, using free agency to shape his team as well as any general manager in the game.
The Broncos front office will do its part, exiting March with one of the few AFC superpowers. The season will ride on Manning's arm, just as it did in 2014.