ENGLEWOOD, Colo. -- It has been 20 years since a 35-year-old Jon Gruden stood on the sideline inside Mile High Stadium during his first trip to Denver as head coach of the Oakland Raiders.

The Denver Broncos' starting quarterback that day, John Elway, was in his final season as a player, one that culminated in a second Super Bowl win. Since then, Elway has been enshrined in the Pro Football Hall of Fame, managed a business empire, returned to football as the Broncos chief football decision-maker -- winning another Super Bowl to close out 2015 -- and has become a grandfather.

Gruden, now in the first season of his second stint as Raiders coach, returns to Denver on Sunday as a 55-year-old who many of league's fans were introduced to as an ESPN analyst on Monday Night Football or challenging draft hopefuls during his QB Camp series.

Elway and Gruden: two guys who didn't have to return to pro football, who had enough money and fame not to, and yet here they are back in the game because they each say they needed to be.

"I don't feel like I ever left football. ... I just didn't have a team," Gruden said. "I wanted to come back because I love the Raiders, I love football, I wanted to help build a championship team."

The Broncos won that first meeting between Elway and Gruden in 1998, 34-17.

"Yeah, it wasn't very fun, it was a nightmare," Gruden said Monday about that game. "They were a great team right ... [at] the height of their run."

The Raiders held a 10-7 lead at one point, but the Broncos were building toward a 13-0 start and a 14-2 finish. They were the best team in the league and the Raiders went on to an 8-8 finish.

"I do remember looking at them as a model of what we wanted to become," Gruden said. "And we took it upon ourselves every day to beat Denver. I think I only beat them once when I was here as the head coach -- on Monday Night Football -- but it was the greatest win of my career as a Raiders coach because I know how far we came in just a few years."

And now it is a desire to compete, a desire to work until each decides when to call it a career, that has lured both Elway and Gruden back to the game.

As Elway put it: "You want to compete. ... I was done playing, after that ['98] season, when I thought about it all after the season was over I felt like that was the right time for me [to retire], physically, mentally. But saying that, that desire to compete doesn't really leave you."

This offseason, Elway said Gruden "was a great coach in this league for a long time" and "that I'm sure it will add to the rivalry we have with the Raiders."

The Broncos current quarterback, 30-year-old Case Keenum, has a history with Gruden as well. Following a college career at the University of Houston he was featured on Gruden's QB Camp leading up to the 2013 draft.

"I've been accused of liking everybody, but I really liked Keenum," Gruden said. "What he did in college is unseen, the type of production he had. ... I told our people a long time ago, when I first came here, I think the free-agent acquisition in pro football this year is going to be Case Keenum. ... His fight, his grit, he gets the most out of himself."

Said Keenum of Gruden: "It was really fun, he really is a grinder. ... Pretty sure he had watched every rep I had ever played in college, found some obscure tape, it was a lot of fun ... enjoyed it."

Keenum was Elway's pick in free agency to lead the Broncos out of last season's 5-11 funk, the first losing season the team has had in Elway's tenure as a personnel executive. And Keenum threw for 329 yards and three touchdowns, to go with three interceptions, in last Sunday's win over the Seahawks.

Gruden's debut, a 33-13 loss to the Los Angeles Rams on Monday night, was a far rockier affair, especially in the wake of the Raiders' trade of a former NFL Defensive Player of the Year in Khalil Mack just before the start of the regular season.

Gruden was asked Monday if his football persona was any different than the one many had seen on television in recent seasons and he reaffirmed why he came back to coaching and the work ahead.

"I don't think it's very much different," Gruden said. "I just like football. I just love, I love the challenges of being back on the field, I love being on a team. Biggest change is I have a scoreboard. And right now the scoreboard is telling me I'm not doing very good."