Andy Ruiz Jr.’s fight this Saturday against Jarrell “Big Baby” Miller is a crossroads fight for two heavyweights who had big futures ahead — only to squander their opportunities.

Miller tested positive for performance-enhancing drugs on multiple occasions, first ahead of a planned 2019 fight with Anthony Joshua for three heavyweight title belts, then again ahead of a planned comeback fight in 2020 with Jerry Forrest.

Ruiz, of course, stepped in for Miller in 2019 and shocked Joshua via seventh-round technical knockout. But in their rematch, Ruiz came in massively overweight and lost to Joshua in a wide unanimous decision.

“That guy had so much potential,” said Tim Smith, the vice president of communications at Haymon Sports, speaking to Kurt Emhoff on the Boxing Esq. Podcast. Ruiz is affiliated with Haymon’s Premier Boxing Champions. “He came like a bolt of lightning and knocked out Anthony Joshua and then didn’t show up for the rematch. Everything was still good for him. Everything was still laid out for him. And then he just sort of squandered a lot of that potential. Hopefully it’s not too late for him to get back on track.”

Getting on track is an ongoing process. Ruiz returned after a 17-month layoff following the Joshua loss, outpointing Chris Arreola in May 2021. He then spent another 16 months out of the ring before winning a decision over Luis Ortiz in September 2022. This fight against Miller, which will be on the undercard of Israil Madrimov vs. Terence Crawford, ends nearly two years of inactivity for Ruiz, 35-2 (22 KOs).

“He’s got his hands full with Big Baby,” Smith said. “That’s a lot of man to be pushing around in the ring. I wish Andy all the best in that fight. Andy’s always had very fast hands. He’s got a good beard. He’s one of the more skilled boxers. And people sort of sleep on his boxing skills, so hopefully he can get the job done.”

Miller is 26-1-1 (22 KOs). He returned to the ring in 2022 after more than three and a half years away. Miller was even heavier than ever, ranging from 328 to 341 pounds on his 6-foot-4 frame. He picked up a few victories and then ran into Daniel Dubois last December, getting stopped in the final seconds of the final round.

“You would expect Big Baby, for as big as he is, to just be knocking people out like Deontay Wilder used to do, but I guess he just doesn’t have that,” Smith said. “He bludgeons people, he beats them into submission, and I guess that’s just as good for a guy that size. He also has had some ups and downs in his career and he’s trying to make it back. He was the one that paved the way for Andy to get that shot at Anthony Joshua. I guess Andy owes him a debt of gratitude, but I don’t think he’s going to be looking to pay it back in the ring on Saturday.”

Follow David Greisman on Twitter @FightingWords2. His book, “Fighting Words: The Heart and Heartbreak of Boxing,” is available on Amazon.