DENVER (AP) -- The Denver Broncos have spent years trying to solve their tight end troubles.
Their inadequate coverage of tight ends and inability to get much production from their own are two of the biggest reasons they've fallen so far from their Super Bowl perch and have been looking up at the Kansas City Chiefs in the AFC West since 2016.
Both problems appeared to be fixed this season thanks to an influx of talent on defense and a return to health of Jake Butt, who missed his rookie season last year after tearing up his right knee in his final game at Michigan.
Yet, Butt's season is over after he tore his left ACL at a walkthrough practice Thursday and the Broncos haven't shown much progress in throttling opposing tight ends, either.
In their opener, the Broncos allowed Seattle's Will Dissly to become the first tight end in league history to top 100 yards receiving and score a touchdown in his NFL debut, one that included a 66-yard rumble featuring four missed tackles.
Butt's third ACL tear was the crushing blow, coming four days before the Broncos (2-1) host the Chiefs (3-0) on Monday night .
''I felt for Jake right away,'' Broncos coach Vance Joseph said. ''He's worked so hard for the last two years to get himself back to this point. He was improving every day. He was making plays for us on Sundays. You can see the special ability this player had and the passion.
''This guy was the same guy every day: happy, fully engaged every day, a very smart football player. It's a shame that it ended that way on that kind of play.''
The Broncos promoted third-year tight end Brian Parker from their practice squad Saturday when Butt joined rookie Troy Fumagalli on IR.
That means the Broncos' tight end group now consists of two undrafted players in Parker and Matt LaCosse and 2015 third-round draft pick Jeff Heuerman, who has just 23 career catches and two touchdowns.
''He's been a good pass-catcher for us,'' Joseph said. ''He's always been a pretty good pass-catcher. Now, without Jake, obviously his targets should go up a little bit. But he's done a great job in the past, especially in the red zone.''
Offensive coordinator Bill Musgrave said, ''We're all just broken up about it.''
His loss is a big blow to the Broncos' special teams, too.
''It's a huge loss,'' special teams coordinator Tom McMahon said. ''He's a great pro, he loves football. I love Jake. This football team loves Jake. How he acts as a man, if my boys can be that guy 10 years from now, I'll be a very proud dad.''
Covering tight ends has been Denver's Achilles heel for two years.
It was a big reason they didn't make the playoffs in 2016 and last year they allowed the third-fewest yards (3,395) in the NFL, but tight ends accounted for 1,023 of those yards - third-most in the league.
After focusing on fixing that all offseason, Dissly's debut was a downer for the Broncos, who also allowed four catches for 49 yards to Oakland tight end Jared Cook the following week and Ravens rookie tight end Mark Andrews' 12-yard TD catch last week.
Up next is Chiefs star tight end Travis Kelce, who had a 133-yard game against the Broncos last year.
''He's just a guy that is hard to put a linebacker on because of his ability,'' defensive coordinator Joe Woods said. ''He has the size to match up with safeties. He's really like a wide receiver and tight end. He's definitely a difficult matchup, but I have a lot of confidence in the guys we have - Justin Simmons and our whole safety crew.
''I think we have a chance to go matchup at times against him and win our fair share.''
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