ALLENTOWN, Pennsylvania – If Ronnie Shields were training Guillermo Rigondeaux in 2017, he would’ve strongly advised against the Cuban southpaw jumping up two weight classes to fight Vasiliy Lomachenko.

That ambitious move proved to be too much for Rigondeaux, who declined to continue after the sixth round in part due to a hand injury. That technical-knockout defeat in December 2017 remains the lone loss on Rigondeaux’s record.

Shields still can’t believe that fight even happened.

“He had no business fighting Lomachenko at 130 [pounds],” Shields told BoxingScene.com on Thursday before a press conference at the Renaissance Allentown. “That was just insane. That was crazy. I talked to him about that and he said, ‘I know, I know.’ But he listened to everybody but himself. He should’ve never been in the ring with Lomachenko. He’s way too small.”

Rigondeaux had boxed only once at the featherweight limit of 126 pounds and almost exclusively at 122 pounds prior to challenging Lomachenko for his WBO junior lightweight title. Ukraine’s Lomachenko (14-1, 10 KOs), now a lightweight champion, had fought four times within the 130-pound division before beating Rigondeaux.

Lomachenko was way ahead on the scorecards when their one-sided contest concluded (60-53, 59-54, 59-54). Rigondeaux had a point deducted for habitual holding in the sixth round.

Miami’s Rigondeaux returned to the super bantamweight division for two fights after Lomachenko beat him. The two-time Olympic gold medalist won both of those bouts by knockout, but the former WBA/WBO 122-pound champion decided to drop down even lower for his fight Saturday night against Panama’s Liborio Solis.

Rigondeaux (19-1, 13 KOs, 1 NC) will make his bantamweight debut versus Solis (30-5-1, 14 KOs, 1 NC) in a 12-round fight for the vacant WBA 118-pound championship. Showtime will air Rigondeaux-Solis as part of a three-bout broadcast from PPL Center (9 p.m. ET/6 p.m. PT).

“[Solis] looks pretty good, but with Rigo’s experience, he’s seen it all,” Shields said. “I think that’s gonna be the difference.”

Shields expects Rigondeaux to make an impact in his new division, even at the advanced age of 39.

“He still looks the same as he did way back,” Shields said. “It’s unbelievable that nothing has changed for him. Everybody that comes into the gym, they look at him and they say, ‘This dude’s not 39 years old.’ They think he’s younger because of the way he fights. He’s so smart and everything is intense. He loves to work hard. He’s an unbelievable fighter.”

In the main event Saturday night, Gary Russell Jr. (30-1, 18 KOs), of Capitol Heights, Maryland, will make a mandatory defense of his WBC featherweight title against Mongolia’s Tugstsogt Nyambayar (11-0, 9 KOs).

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.