Sounds like you have had a very productive life! Your son is very lucky.

Encourage the education. But there are loads of good careers that don’t need university degrees.
And all the while, he can try and achieve his dream.

From personal experience, university wasn’t useful for me - other than giving me time to figure out what I don’t want to do, and meeting friends that are still friends to this day.
But I could’ve easily done an apprenticeship, or gone straight into some industry/company. Some days, I wish I had. Other days, I wouldn’t want to be doing anything other than what I am atm.

Dream case, he makes it.
Best case, he figures out what he wants to do by 21.
Worst case, he’s still figuring it out when he’s 25.

I wasn’t making decent money until I was late 20s. Even now, I can’t guarantee I have enough work next year. It’s extremely likely, but I’m self employed so…
Knowing my folks will still support me means I can continue pursuing interesting, useful and innovative things, even in my 30s - even tho that’s not longer required.

Maybe talk to some of your contacts in the football industry.
See if they have similar “football or nothing”, or if they had backup plans.
Talk to some managers, coaches, sports scientists, medics etc.
Ask them how they would get into pro football. Ask them what happens to pro-football aspiring players that don’t make the cut.
Use your experience and connections to help and support your son. And be there if it doesn’t work out.
You might know better, but he still has to learn. The best lessons are mistakes.