The Broncos (8-7) close their disappointing season late Sunday afternoon at home against Oakland (12-3).
Several coaches and players said over the last week that Kubiak, the former Ravens offensive coordinator, hasn't informed them of any retirement plans. The Broncos didn't immediately return messages Sunday morning in regards to rampant speculation over Kubiak's future.
Kubiak, who has two years left on his contract, was evasive when asked Friday about his health and coaching future.
“Why, do I look bad?” Kubiak said, smiling. “There will be time for reflection and all of that stuff next week, but right now it's time to focus on what we're doing.”
The 55-year-old Kubiak suffered a complex migraine on Oct. 9 following Denver's loss to Atlanta, his second health scare in three seasons. Doctors ordered him to take a week off and he hasn't appeared to have any health issues since.
He also suffered a mini-stroke at halftime of a game against Indianapolis in 2013 when he was coaching the Houston Texans.
He was fired at the end of that season and had a terrific comeback in 2014 as offensive coordinator in Baltimore, where he had planned to stay until Broncos GM John Elway called him following John Fox's ouster.
Calling it a “game-changer,” Kubiak stepped back into the pressure cooker on Jan. 19, 2015, when he was named the 15th head coach in Denver, where he spent 13 seasons either backing up Elway at quarterback or drawing up blueprints as his offensive coordinator.
He said at the time that his health scare in 2013 taught him to rely more on those around him. He also said he wasn't worried about the pressure of the Denver job, noting he thrived amid high expectations as a player from 1983-91 and then serving on Mike Shanahan's staff from 1995-2005, coaching the Texans from 2006-13.
Last season, he deftly managed injuries at quarterback, edge rusher and left tackle to lead the Broncos to their third Lombardi Trophy even though both Peyton Manning and Brock Osweiler struggled to run the offense.
Kubiak's offensive philosophies are rooted in Bill Walsh's West Coast system featuring the zone-blocking schemes that the Broncos fine-tuned in the 1990s and 2000s. But in both of his seasons in Denver, the Broncos have stumbled offensively, unable to run the ball and get much production from the tight ends.
With four new starters along the O-line this season, the Broncos again sputtered behind poor blocking and a battered backfield, where C.J. Anderson, Andy Janovich and Kapri Bibbs ended up on IR.
Neither Trevor Siemian nor Paxton Lynch settled in at quarterback. Siemian suffered injuries to both shoulders and his left foot, forcing him to miss 2 1/2 games. In those games, Lynch showed he was far from adapting to the pro game.
If Kubiak steps down, possible replacements include Miami defensive coordinator Vance Joseph and Atlanta offensive coordinator Kyle Shanahan.
Even if Kubiak returns, there are expected to be changes to his offensive staff after a season-long, head-scratching inability to start fast.
The Broncos have scored an NFL-worst 33 first-quarter points and had just one sustained touchdown drive in the first quarter all season.
The Broncos also missed run-stuffers Malik Jackson (free agent departure) and Vance Walker (season-ending knee injury in camp) and their run defense slipped from top-3 all the way to 29th in the league in 2016.
Sunday's game against the Raiders is the first for Denver since 2010 without any playoff implications. Immediately following Denver's loss at Kansas City on Christmas that eliminated it from the playoff chase, Kubiak told his team the finale Sunday would be all about looking toward the 2017 season.
He plans to use both his young quarterbacks against the Raiders following a week that included only walkthroughs with no helmets or hitting.