With Marvin Mims Jr. expected to play an important role in his first NFL regular-season game Sunday, his high school coach texted him with some news.

“I told him that our son just did our fantasy draft and that you were the first non-quarterback taken,’’ said Jeff Rayburn.

Rayburn, who coached Mims at Lone Star High School in Frisco, Texas, didn’t deny it was a bit of a “homer pick” his 10-year-old son Cade made for the Team Rayburn fantasy outfit. Then again, Rayburn remembers well what the Broncos rookie wide receiver once did in high school.

In his senior season of 2019, Mims set a national single-single season record with 2,629 receiving yards and broke the Texas career mark of 5,485. He then went on to Oklahoma, where he had 54 catches for 1,083 yards last season for the Sooners, and in April was a second-round draft pick by Denver.

“I think he’s going to light it up this season,’’ said Rayburn, who said the two players Cade drafted ahead of Mims were Buffalo quarterback Josh Allen and Kansas City quarterback Patrick Mahomes.

The speedy Mims’ first opportunity to make an impact in a regular-season game will be in Sunday’s opener against the Las Vegas Raiders at Empower Field at Mile High. He will be at least Denver’s No. 3 receiver behind Courtland Sutton and Jerry Jeudy and would move up to No. 2 if Jeudy can’t play due to a hamstring injury.

Jeudy was hurt Aug. 24 in a joint practice with the Los Angeles Rams. He was listed Friday as questionable for Sunday’s game.

“I feel good,’’ the 5-foot-11, 184-pound Mims said of his impending debut. “I just want to go out there and do the best I can. … I want to play in the NFL for a long time and just be a great teammate and go out and play my game.”

Mims, 21, will have plenty of support Sunday. His father, Marvin Mims Sr., said 19 family members will be on hand. In addition to Mims Sr. and his wife Rhonda, the group will include Mims’ sister Raven, 29, and his brother DeAndre, 25.

“Everybody is super excited,’’ said Mims Sr., who said he’s never missed a game his son has played at any level. “Everybody is extremely happy for him because he’s been a good kid. He’s done everything the right way and just to be able to see him live out this dream and see things really pay off for him has been a blessing.’’

Mims Sr. looked back at when his son first began to play football. He was a wide receiver and running back for the Frisco Packers starting in the second grade.

Mims showed plenty of flashes early of what was to come.

“When he was with the Frisco Packers, by the time he was in the third through the fifth grade, they were throwing like 30- to 40-yard passes to him and he was catching balls coming over his head,’’ said Mims Sr. “He was the only kid in the league catching passes like that.”

Despite his early success in football, it looked for a while as if Mims might pursue basketball as his primary sport. He played on a top-notch AAU team and enrolled at Legacy Christian Academy in Frisco in ninth grade with the primary purpose to play basketball.

After one year at the school, though, the undersized guard realized that football might be a better path. He transferred to Lone Star High School to play for Rayburn.

“I told him that he could be the best player to ever come out of here, and he did that in a big way,’’ Rayburn said.

Mims did play basketball for the Rangers as a sophomore and junior. But it was on the football field where he truly excelled.

As a senior, Mims caught 117 passes and had 32 touchdowns. He continues to be amazed when he looks back on those statistics.

“It’s still crazy. It’s ridiculous, but it’s pretty cool to still have (the records),’’ he said. “People still ask me about it. I had a great offensive coordinator in Mark Humble and head coach Jeff Rayburn believed in me and we had a great quarterback (in Garret Rangel, who is now at Oklahoma State). We were slinging the ball and it just all came together.”

Mims, who was a top student with a grade-point average of about 3.7, originally committed to play at Stanford. But Stanford at the time did not allow high school recruits to enroll in January if they graduated in December, as Mims did. So for that reason and to stay closer to home, Mims ended up instead going to Oklahoma.

Mimis made an immediate impact with the Sooners. In his first game, he caught three passes for 80 yards and a touchdown.

“I had a (58-yard) touchdown on my first play,’’ he said. “I remember it like it was yesterday.”

Two of his Broncos teammates were also with Mims at Oklahoma in linebacker Nik Bonitto and safety Delarrin Turner-Yell, who are both in their second season. Turner-Yell said Mims at Oklahoma “handled everything the right way” and was wise beyond his years.

Turner-Yell now has the stall next to Mims’ in the Broncos locker room.

“When we drafted him, I asked the equipment guys, ‘Can we put him right here?’’ Turner-Yell said. “I just wanted to make him a little more comfortable coming into the league. … He was very good (at Oklahoma) and I feel like he’ll do the same thing here.’’

Mims had wowed the Broncos by running the 40-yard dash in 4.38 seconds at the combine. But when he was drafted, it looked initially as if they wanted him as a punt returner for his rookie year and that he might have to wait his turn to get a lot of work at wide receiver. But then the Broncos began to lose receivers, most notably starter Tim Patrick being sidelined for the season with a torn Achilles suffered early in training camp and KJ Hamler being released after being diagnosed with a minor heart irritation. Hamler could return to the team during the regular season.

Mims missed some time early in training camp with a hamstring injury and sat out the preseason opener at Arizona. But he returned for the final two preseason games, which included making a 50-yard catch against the Los Angeles Rams in the finale.

“Marvin’s a real professional,’’ said Broncos quarterback Russell Wilson. “I think Marvin’s ability obviously is to run, his ability to catch. He made some great plays throughout the preseason. … He’s going to have a great rookie year. I think the best thing he can do is continue to show up every day with the right mindset knowing there’s going to be battles (and) ups and downs. It’s a journey.”

Broncos coach Sean Payton said Mims will “have a role” both as a receiver and returner to start the season. Mims, who ranked eighth in the nation last season with a punt-return avarege of 12.5 yards, is listed as first team on the depth chart as both a punt and kickoff returner. While he does figure to be Denver’s punt returner, it’s not certain that he also will return kickoffs.

However it shakes out, whenever Mims has the ball in his hands, there’s a chance of exciting things happening.

“Speed can open up a defense,’’ Mims said. “Guys are kind of scared of speed. Whatever Coach Payton draws up and whatever my role is in this offense, I’m going to do it to the best of my ability to use my speed as well as I can.”

Mims Sr. said he can’t recall in high school Mims ever going against a defensive back who was faster than him. Rayburn said Mims’ speed helped him shatter records but that he always remained a “super humble, hard-working person.”

Now, Rayburn is proud to have Mims back on his team even though it is fantasy football.

“As long as we’ve got Marvin on our team, we’ll be all right,’’ he said.