Former three-division world titleholder Abner Mares has an undisclosed medical issue that has prevented him from being licensed by the New York State Athletic Commission and forced his June 25 shot at featherweight titlist Jesus Cuellar to be canceled on Friday.

But multiple sources with knowledge of the situation told that the fight was canceled because Mares could not pass two NYSAC-administered eye exams this week during which his uncorrected vision in at least one eye was worse than the state’s minimum required 20/200.

Mares has had eye problems in his career, including suffering a career-threatening detached retina while preparing for a fight in 2008. Mares had surgery and sat out for 11 months unsure if he would ever fight again.

The fight with Cuellar loomed as a good one in the loaded 126-pound division and was scheduled to take place at Barclays Center in Brooklyn, New York, as the co-feature of the CBS-televised card headlined by welterweight titleholder Keith Thurman (26-0, 22 KOs) taking on former titlist Shawn Porter (26-1-1, 16 KOs).

Lou DiBella, who is promoting the card, issued a statement on the Cuellar-Mares cancellation but declined to discuss the specifics.

“Regrettably, due to a medical issue that renders former three-division world champion Abner Mares presently unable to fight in New York State, the Cuellar vs. Mares fight has been cancelled and will be replaced on the telecast next Saturday, June 25,” DiBella said in the statement. “Abner’s condition is in no way life-threatening, nor was it revealed in a blood or urine test; there was no use of any drugs, including PEDs or other banned substances.

“In honoring Abner’s right to medical confidentiality, no further information will be released on this situation unless he chooses. An announcement will be forthcoming with respect to the replacement bout that will open the Showtime Championship Boxing on CBS, presented by Premier Boxing Champions, broadcast.”

The 29-year-old Cuellar (28-1, 21 KOs), of Argentina, was due to defend his secondary featherweight title for the third time against former bantamweight, junior featherweight and featherweight titleholder Mares (29-2-1, 15 KOs), a 2004 Mexican Olympian living in Los Angeles.

Mares is coming off a spirited split-decision loss challenging Leo Santa Cruz for a vacant featherweight world title last August at the Staples Center in Los Angeles. During that fight, Mares suffered cuts around both eyes due to accidental head butts.