Mike Glennon didn't have to be a good sport about this.

Last offseason, he signed a three-year, $45 million free agent contract with the Bears, hoping to prove he was a starting-caliber quarterback. The opportunity lasted four games before he was replaced by rookie Mitchell Trubisky, and Chicago cut him in March.

Now Glennon is on the Cardinals, with the understanding he is once again a backup. That's quite the mental roller coaster in a 15-month span, but the 28-year-old assessed it calmly near the end of offseason work in June.

"Everyone wants to be out there playing, but at quarterback it's a unique situation because only one guy can play," Glennon said. "That dates back to my time in college when I was behind Russell Wilson (at North Carolina State) for three years. You feel like you're a pretty good player yourself, but there's only room for one guy. You just have to keep everything in perspective and realize I'm still living the dream."

Glennon has made a reported $21 million over the past two years, so certainly there are worse situations. Even so, elite athletes have an unquenchable desire to compete, and a return to the bench is tough.

If there is any bubbling angst within Glennon, coach Steve Wilks hasn't seen it. He spoke highly of Glennon's maturity.

"A pro's pro," Wilks said. "He really is. He understands his role and he's very passionate about what he does. He's out there competing. If the opportunity arises, he's going to be ready to play. He's a team player, and that's what I like about him."

After feeling well-prepared for last year's free agency, the 2018 offseason was a whirlwind for Glennon. He was released by the Bears on March 14 and signed with the Cardinals two days later. A pre-existing relationship with General Manager Steve Keim -- a fellow North Carolina State product -- helped tilt the scales in Arizona's favor.

"I felt comfortable with my relationship with Steve, and I'd been in an offense similar to (offensive coordinator) Mike McCoy's in the past, so it made sense for me," Glennon said.

Sam Bradford is expected to go into the season as the starter, and first-round pick Josh Rosen – drafted six weeks after Glennon signed -- is now the quarterback pegged to lead the franchise into the future. It leaves Glennon somewhat in purgatory, but after backing up Wilson, Josh McCown and Jameis Winston in recent years, he knows the drill.

"I've been in that backup role more than the starter, so I'm comfortable with it," Glennon said. "I understand my role, and what my job is to help this team. That's to both compete and help these two guys out."

While it's never optimal, the Cardinals have been forced to lean on reserve quarterbacks frequently in recent years. Drew Stanton did a great job filling in for Carson Palmer during his five-year tenure in Arizona, winning nine of 13 starts.

Training camp will sort out whether Glennon is the main backup when the season begins, or if he will drop to No. 3 behind Rosen. If he does see the field at some point, it won't be with any of the fanfare of a year ago, but Glennon pledges to be equipped.

"That's what I feel like I've done over the past few years, always prepare and be ready for that opportunity," Glennon said. "When I was the backup in Tampa, it never really came. You just never know. I know Arizona has had that come up a lot recently. You have to go in with the mindset of, 'I have to be ready to go.'"

If that opportunity doesn't come in 2018, Glennon hopes to add value in other ways, pushing the fellow quarterbacks in practice and contributing in meetings.

The one thing he said won't be an issue is ego, even though Glennon, Bradford and Rosen all started season openers a year ago and two of them will begin this year on the bench.

"Honestly, I don't feel it's ever been an issue anywhere I've ever been," Glennon said. "You grow close, you spend a lot of time together, and you want to see the other guy succeed as well. I feel like there's always healthy relationships and an unwritten understanding that we're going to push each other, but we're here to help one another out as well."