NORMAN, Okla. – These are the best days of Lincoln Riley's career. Are they also his last at Oklahoma?

It's hard to imagine life getting better for one of the brightest coaching minds in the game. It's also hard to measure the anxiety within the program Riley is leading.

The name of Oklahoma's second-year coach has been mentioned prominently in NFL circles. That is to be expected, but it is also a frightening realization for OU fans that have seen the best two-year start by a Sooners coach since Barry Switzer (1973-74).

The 35-year-old Riley is arguably the best play caller in college football. He took over a championship program from Bob Stoops 18 months ago … and kept winning championships.

No. 4 Oklahoma plays in its second consecutive College Football Playoff under Riley this Saturday when it faces No. 1 Alabama in the Orange Bowl.

Could that possibly be Riley's last game with the Sooners? Probably not … at least for now. Riley has 30 years (or so) left in his career. If he's going to the NFL someday, he would be wise to pick the absolute best setup out there. Translation: A team with the ability to win immediately.

Still, there's enough NFL buzz to make OU fans uneasy. Cleveland Browns general manager John Dorsey has attended Oklahoma's last two games. Riley's name has been linked to the Dallas Cowboys, too.

"Lincoln has Oklahoma really primed," said Dusty Dvoracek, a two-time All-Big 12 nose tackle under Stoops. "He's in such a good situation. The only job -- the Dallas Cowboys -- is the one that would somewhat worry me. He's still a Cowboys fan. That's one of the top 10 jobs in football. Do you want to deal with Jerry Jones if they back up the Brinks truck?"

Ian Rapoport of NFL Network reported last month that Jones and son Steve Jones had an "affinity" for Riley to replace Jason Garrett should a change be made in Big D. 

You could almost feel Sooners everywhere flinch after Riley has led Oklahoma to two playoff berths, two Heisman Trophy winners and the highest-scoring offense in college football in five years. That speculation has reached all the way to the office of OU athletic director Joe Castiglione.

"From our perspective, we are not in competition with the NFL," Castiglione recently told CBS Sports. "That's an entirely different structure. Our focus is try to make this the best college job. That involves so many various aspects to a coach considering this is the place they want to be. The quality of life his family has, the support staff they're given. I know how people want to take it that way sometimes."

Castiglione just got through this sort of speculation for years with Stoops, whose name popped up just about annually for college and NFL jobs, including one year into retirement before this season when the Chicago Bears had an opening.

It all started 2000, Stoops's second season at OU.

"I remember standing on the field at the Orange Bowl," Castiglione said. "ESPN folks came up to me because a story had just broken. The Ohio State University had just made a coaching change. Bob Stoops was their No. 1 candidate. We are literally minutes before the team comes running out for the kickoff. They told me they were going to go live with it sometime during the game. They wanted me to comment.

"'We're playing for the national championship. That's our comment and that's our focus.' The Cleveland Browns were open at the about he same time."

Oklahoma went on to beat Florida State for the school's seventh national championship. Stoops stayed 15 more years.

"He could almost count on one or two pro jobs -- almost every year -- to seek his interest," Castiglione said of Stoops.

The speculation about Riley isn't going to die down soon.  There is actually a clause in his contract that requires the coach to alert the school if he is contacted about another job. 

That has not happened yet, Castiglione said. That also would not preclude suitors from making third-party contact (through an agent).

"I always want to be truthful,'' Riley said last week. ''And the truth for me is [that] I love Oklahoma. I love coaching here. I love college football. I certainly don't have that itch right now. I don't know if I ever will.

"I'm never going to be a guy that's going to stand up here and say, 'No way, no how will any of these things ever happen.' I don't know that. I know right now I could [not] care less about the NFL.''

End of story? Riley and Oklahoma are caught in the middle of a revolution of their own making. The NFL has adopted many of the spread and RPO concepts perfected in college.

"Patrick Mahomes, Andy Reid, look at Baker Mayfield," Dvoracek said, referencing the Kansas City Chiefs power couple and Riley's former quarterback with the Browns. "All of it is trending toward Lincoln Riley and that style of offense."

This is Riley's fourth season calling plays at Oklahoma. It's hard to believe he was East Carolina's offensive coordinator in 2014.

The convergence of circumstances also includes NFL success by a coach at a similar age to that of Riley. Sean McVay, 32, is 23-8 in his first 31 games with the Los Angeles Rams. Then throw in Carson Wentz (and Nick Foles) winning the last Super Bowl using coach Doug Pederson's RPO concepts.

"A lot of people like to live in a black and white world, it's either a player or a coach," said Steve Palazzo, Pro Football Focus senior analyst. "The NFL is looking for offense. It's really an offense-driven league right now."

Offense has driven college football for at least the last 15 years, so much so that NFL types are willing to overlook Oklahoma's defense -- 108th nationally, the worst ever to play for a national championship.

"Lincoln is probably the brightest offensive mind not only in college football but in all of football," Dvoracek said. "That being said, I'm a defensive guy. I truly believe that deep down you've got to get stops. You can be really good on defense and give up 40 tackling and winning the line of scrimmage. We've seen that from Alabama and Clemson."

Not so much Oklahoma under Riley. He fired Mike Stoops as defensive coordinator after an October loss to Texas. The defense got worse.

Not a concern for the NFL?

"Look at what Sean McVay did. He got [veteran NFL defensive coordinator] Wade Phillips," Palazzo said. "He can run the defense. [The head coach] can run the offense."

Too much too fast in all this Riley speculation?

"There's something about living in Oklahoma, being head coach at the University of Oklahoma is a really special platform," Castiglione said. "At the same time, you can really be yourself."

And should Riley leave either soon or one day in the distant future? Oklahoma will continue to prosper.

"It's going to stand up against the fiercest of competition," Castiglione added. "Barry Switzer had the great line about Oklahoma: 'If someone sees themselves going someplace else, there will be an enormous line at the front door to get this job.'"