When Tanner was just 9 years old, Ryan Gentry knew that his son had a promising future.

"Watching him run on the football field, doing crazy things and making moves that most kids can't at that age, I just knew that he was something special," Ryan said.

Still, as he sat in the stands at Soldier Field on a Thursday night in early August, the moment seemed surreal.

There on the gridiron below was his now 22-year-old son, Tanner Gentry, playing in his first NFL game against the team he grew up rooting for.

"Being a native of Colorado, being a Denver Bronco fan all these years, I'll definitely always be a fan," Ryan said. "But, when your son plays for Chicago, it kind of trumps that."

An alum of Grandview High School in Aurora, Co., and then the University of Wyoming, Tanner Gentry signed with the Chicago Bears as an undrafted free agent in April. The wide receiver will hope to make the Bears' 53-man roster by the start of the season.

His path to that goal included the Bears' first preseason game against the Denver Broncos on Thursday. It was his first chance to show a national audience, and the Chicago coaching staff, what he can do at the highest level when the lights are on.

You can bet a lot of them were intrigued, since Gentry had already been impressing people in camp.

But now, it's about his play in a game situation. So, of course his family and friends were there to support Tanner on his big day.

"We have 10 or 12 people up here for his first preseason game," Ryan Gentry told 9NEWS before kickoff. "We're just a big family. We're close. He's got a lot of supporters, and we're just here to root him on and basically be a fan."

All their cheering in the crowd might have paid off. Tanner had his first NFL catch, a 13-yard reception, in the fourth quarter that helped lead Chicago to a field goal to make it 17-10 Bears.

His father is hoping it's just the first of many catches in a successful pro career.

"He's proved people wrong his whole life," Ryan said. "I think it can go as long as he wants it to go. He knows that if he keeps working hard, good things will happen."

The preseason is a stressful time for all rookies, especially undrafted free agents. The difference between being the final player cut and the 53rd guy on the roster can be hundreds of thousands of dollars, and perhaps millions over the course of a career.

One catch, one play or even one small moment could be life-changing. So, there are a lot of uncertainties for Gentry right now. But, one thing is certain. His family will be there by his side every step of the way.