Sports Illustrated has put out a piece on the “Biggest gut-punch loss” for each and every franchise, the Broncos included.
The game that the author the piece, Doug Farrar, picked is an interesting one – a game that stopped the Broncos from their playoff run in 1996 when the team fell at home to the Jaguars.
Denver Broncos: Jan. 4, 1997, AFC divisional round—Jaguars 30, Broncos 27
John Elway was the losing quarterback in three Super Bowls earlier in his career, and he actually had his most productive seasons a few years after Denver’s championship chances dried up for a while. Things started to look up in 1995, when owner Pat Bowlen hired Mike Shanahan, Elway’s old offensive coordinator, as the new head coach. The Broncos went 8–8 in 1995, but jumped up to 13-3 in 1996. With one of the best overall teams in the NFL, it looked like Elway might get another shot at the Super Bowl.
But in what turned out to be perhaps his most agonizing postseason defeat, Elway’s Broncos were stunned by the Jaguars—a second-year expansion team—after starting with a 12–0 lead. Jaguars QB Mark Brunell proved to be a lot like Elway had been in earlier years, an accurate passer who could outrun pressure, and the Broncos couldn’t measure up. Denver won two Super Bowls in the next two seasons, a feat made all the more impressive by the fact that this loss was such a psychological hit.
The Broncos got their revenge against the Jaguars a season later, and went on to win two straight Super Bowls.

Berdj J. Rassam
July 23, 2015 at 11:10 pm
Yes, that was a tough loss for the Broncos.