AJ McCarron, who has four starts in his four-year NFL career, became the league’s hottest available quarterback Thursday when it was ruled he is eligible for unrestricted free agency.

The Broncos will be interested in checking him out. Then again, in their current state they'll be watching film of all available quarterbacks.

McCarron was 36-4 with two national championships in three seasons as Alabama’s starting quarterback, yet he wasn’t selected until the fifth round of the 2014 NFL Draft by Cincinnati.

The only time he had significant playing time with the Bengals was late in the 2015 season in place of the injured Andy Dalton. McCarron had three regular-season starts, including one against a Broncos’ team that went on to win Super Bowl 50.

McCarron played well in Denver but Brock Osweiler played better in a 20-17 Broncos victory. A little more than three years later, the Broncos are looking to replace their quarterback likes of Osweiler, Trevor Siemian and Paxton Lynch with a franchise-type guy.

McCarron’s stock has soared in part because of his encouraging brief audition in 2015 – besides his three regular-season starts, he played well in a playoff loss to Pittsburgh -- and because the Cleveland Browns were willing to acquire him last season for the hefty price of a second- and third-round draft pick.

The trade fell through and now McCarron is expected to become a free agent – providing Cincinnati doesn’t apply the franchise tag on him.

McCarron would not replace Kirk Cousins or Case Keenum on the Broncos’ priority list. But a case can be made McCarron now heads the B group of available quarterbacks.

Here is how I rank the list of quarterbacks who might be available either through trade or free agency when the 2018 league season opens on March 14:

A Group

1. Drew Brees, Saints

He is 39 and a half season away from becoming the NFL’s all-time leader in career passing yards. He’s also a Super Bowl champion.

However, Brees has let it be known he will only play for New Orleans. Until he re-ups, though, he is officially the top player available.

2. Kirk Cousins, Washington

After averaging 27 touchdowns passes against just 12 interceptions in his past three full seasons as a starter, he will play at the relatively young age of 30 in 2018.

His 26-30-1 career record, though, will bring pause to teams who understand it will take no less than a five-year, $140 million contract -- $28 million per – to sign him.

3. Case Keenum, Vikings

Through his first five NFL seasons, Keenum was 9-15 as a starter with 24 touchdown passes against 20 interceptions.

In year six with Minnesota, Keenum was 11-3 – plus an exhilarating second-round playoff win against Brees’ Saints – with 22 touchdown passes against just 7 interceptions.

Keenum will turn 30 on Saturday. His first NFL head coach was Broncos’ front-office advisor Gary Kubiak when both were employed by the Houston Texans in 2012-13.

B Group

1. AJ McCarron, Bengals

If longtime Tampa Bay backup QB Mike Glennon got a three-year, $45 million deal with the Bears last year, McCarron’s contract floor will be $16 million a year.

2. Teddy Bridgewater, Vikings

A solid, young, NFL starter – until a devastating knee injury caused him to essentially miss the past two seasons. It’s unlikely the Vikings will allow both Keenum and Bridgewater to walk away. They’ll keep one.

3. Tyrod Taylor, Bills

He and backup Paxton Lynch could operate a similar, offensive system of play-action from the shotgun while the Broncos groom the rookie quarterback they would take with their No. 5 overall draft pick.

4. Jay Cutler, Dolphins

He’ll turn 35 on April 29. There is some question about his commitment to the game after he nearly retired last year, but he looked pretty good in a 35-9 rout of the Broncos in early December.

He would be ranked higher in the B group if not for his bridge-burning past with the Broncos.

AB Group

1. Nick Foles, Eagles

In a group unto himself, Foles is either a B-lister journeyman backup or A-list Super Bowl MVP.

Has one year and $7 million left on his contract which is good backup money, but inexpensive as reigning postseason superstars go.

With Carson Wentz returning from his knee injury, the Eagles could ask for a first- or second-round draft pick from any team wishing to acquire Foles in trade.

C Group

1. Sam Bradford, Vikings

A No. 1 overall draft pick talent who is still an accurate passer but has also essentially suffered three, season-ending knee injuries.

Can’t be counted on as a No. 1 QB.

2. Josh McCown, Jets

A quintessential journeyman starter who can bring respectable quarterback play to struggling teams. He’ll turn 39 on July 4.