John Elway says he does NOT believe Colin Kaepernick is being blackballed by the NFL over his national anthem protests ... but says he's not really sure if the QB can still compete in the league. 

John and his smokin' hot wife Paige (a former Oakland Raiders cheerleader!) were in D.C. when we asked why he thought the ex-49ers quarterback is still unemployed. 

Elway is the GM and executive vice president of football operations for the Denver Broncos -- a team that could use a QB right now -- but when it comes to Kaep, Elway says he hasn't been studying up. 

When we asked if Kaep could still play, John replied -- "I don't know. I haven't been close enough to him to be able to tell."

Of course, Colin is currently unemployed and some believe he could end up in Denver ... if John decides he's worth a look.