Hall of Fame linebacker and former NFL football coach Mike Singletary will partake in the new Alliance of American Football league. (Daniel Mears/Associated Press)

If professional football is in the midst of an inexorable decline — the NFL, some doomsayers sayeth, might be a sporting dinosaur by century’s end * — then how is it possible there are two new professional football leagues aiming to debut by 2020?

* I know I’m not going to make it to century’s end — unless the daily multivitamin I take really, really overperforms — but I also believe it is possible NOBODY makes it to century’s end. The planet may not be here any more, though if it does perish, somehow I think Ryan Seacrest still survives.

Say hello to the Alliance of American Football (AAF), set to debut in February 2019, and the XFL (XFL), set to debut in February 2020, not to be confused with the XFL (XFL) that operated for one somewhat tortured season in 2001.

(I’ve been thinking of rebooting Strat-o-Matic Football or even electric football. Biggest advantage to watching electric football live? Booger McFarland can’t block your view.)

The AAF will have franchises in Atlanta, Birmingham, Ala., Memphis, Orlando, Phoenix, Salt Lake City, San Antonio and San Diego, cities with the highest concentration of TGI Fridays in America. It is the brainchild — I use “brain” and “child” loosely here — of producer Charlie Ebersol, son of Dick Ebersol, one of the minds behind the original XFL.

Coaches will include former NFL top guns Brad Childress, Mike Martz, Mike Singletary, Steve Spurrier and the late Weeb Ewbank. Michael Vick has signed as offensive coordinator of the Atlanta franchise, pending any conflicts in schedule with his new dog fighting ring.

The AAF will consist largely of undrafted college players and other NFL rejects. The league held a quarterback draft last month, with the R*dsk*ns’ latest broken-leg candidate, Josh Johnson, selected No. 1 by San Diego.

AAF games will be on the CBS Sports Network (CBSSN), with the title game on CBS. I don’t know if this baby will fly, but if CBS has a studio show called “The AAF Today” with Norman Esiason on board, I give the league two years.

To differentiate from the NFL, the AAF will have no kickoffs, no extra points — just two-point conversions — no TV timeouts and no viewership through 2025.

(You can find a Cracker Barrel in Manhattan easier than you can find CBSSN on your cable system.)

The AAF wants to appeal to fantasy football fans who can’t feed their habit after the NFL ends; similarly, fantasy opera fans long have complained they have nowhere to turn each spring after The Met completes its season. The league will launch a smartphone app in which fans can stream games, play fantasy football and make long-distance calls to friends and family.

Meanwhile, the XFL — Vince McMahon’s second foray into violent, non-wrestling near-entertainment — will have franchises in Dallas, Houston, Los Angeles, New York, St. Louis, Seattle, Tampa and Washington. The league, I believe, will consist of Hulk Hogan, Steve McMichael, Ray Lewis and 124 scantily clad cheerleaders.

The best thing about a Vince McMahon enterprise? You know it will be all class.

Each team will have a quarterback by summer, if there are any left after the AAF picks through the remains of the McCown family.

(Not surprisingly, Amazon announced it is opening a quarterback warehouse in Blytheville, Ark., next winter, expected to create dozens of jobs in the area.)

Incidentally, a third new league is also trying to launch, Pacific Pro Football, designed for college-age athletes who want to play football but do not want to attend school. Hmm. I thought they already did that at Alabama, Ohio State, Maryland and USC.

You know what really scares Couch Slouch? That one day Major League Soccer (MLS) might have a rival league. Actually, I’d call it Really Major League Soccer (RMLS), and, with any luck, an equal number of people won’t watch it on TV.

Ask The Slouch

Q. I’ve heard that in the Week 11 Bengals-Ravens game, with 12:46 left in the third quarter, there was a kick return and “illegal block in the back” was NOT called. I seriously doubt this, but can you weigh in? (Alan Hlava; Mazeppa, Minn.)

A. I have reached out to Mike Pereira, but, unfortunately, this was not a Fox game, so he declined to comment.

Q. If the New York Mets keep adding players like Robinson Cano to a roster that already includes Yoenis Cespedes, will slow motion replay on their telecasts eventually be considered redundant? (Dan Cantwell; Albany, N.Y.)

A. You will run to the bank with your 10 bits faster than they run to first base.

Q. Is it true that the NFL is changing its player injury-availability categories to “active,” “accused,” “indicted” and “convicted”? (Terry Golden; Vienna, Va.)

A. Pay the man, Shirley.

Q. Since Bryce Harper will be apparently be making more money than God, is it time to renegotiate God’s contract? (Tom Jessen; Applegate, Calif.)

A. Pay this wise soul, too.

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