Alvarez -- who was the lightweight champ in UFC and Bellator -- LOVED the way Ben Simmons applied a perfect rear-naked choke on Karl-Anthony Towns ... but thinks there's room for improvement.

So, the Philly native tells TMZ Sports he reached out to Simmons and the two will connect in the next few days for some real MMA training so the team can step up their fight game.

Eddie also has some advice for Karl-Anthony, too -- pointing out the MAJOR mistake Towns made during the brawl that left him fully exposed.

Bottom line, Eddie says he was super IMPRESSED with Ben's fight skills -- same with Joel Embiid -- and he cant wait to hit the mats with the guys.