At the end of COM, Carmen and Vincent were already arguing and fighting like a break up was coming fast.
Carmen meets a better, smarter hustler at that same tournament and ends up dumping Vincent for him.
Vincent is broken up but wants to win so badly that someone easily hooks him up with drugs- he beats his gambling match that night, beats Eddie, wins the tournament, and gets himself a drug addiction to go with all of that money. Now that he has no one with any sense controlling him, the drugs take over and he lands in jail (any number of interesting charges).
Time in and out of prison, over and over, finally gets some of the attitude knocked out of him, he eventually gets clean, and he learns some sort of trade. Cold and prison hardened, he finally breaks the cycle and decides to be the straight and narrow non pool player.
A lunch hour? After work beers with coworkers? gets him back into a poolroom again, and he finds he still has some skill left. And there's a young kid acting up a storm, just like he did. He remembers himself when he was young, and decides he's going to take this kid under his wing and try to teach him and guide him.
Plot twists ahead: Vince isn't allowed to leave the state on his probation terms, but he and the bebe kid go on a multi-state road trip anyway; there are new drug temptations; Carmen is still strong and heavy in the big money pool scene, and she has a soft spot for Vincent and the memories of youth.