The 36-year-old middleweight was outpointed by The Destroyer, 29, in their second meeting, and Next Gen has now admitted a series of health problems affected him throughout fight week and contributed to his flat performance.
Posting a hospital video and statement on X, he said the issues had “caught up” with him during the Benn fight.
Speaking to fans, he said: “I will not box again until I’m back to 100 per cent and I don’t know when that will be.
“But one thing’s for certain. For the fans that have supported me through thick and thin, I will do everything in my power to make sure that one day, the old me makes a big comeback.”
The rematch saw both fighters compete under a strict rehydration clause, limiting weight gain to 10lb between the official weigh-in and fight-morning checks.
Eubank Jr. had hinted at retirement in the build-up to the fight, but later clarified that he intended to continue his career and still hopes to secure a world-title opportunity.
At present, there are no plans for a trilogy bout with Benn, as the contract covered only two fights.
Eubank had been heavily outclassed on the night, and his promoter Ben Shalom recently claimed Next Gen was a “shell of a man” by the time he stepped into the ring.
Speaking to talkSPORT, Shalom said: “That was not Chris Eubank Jr in the ring … I think anyone with any sort of brain can see that wasn’t Eubank Jr., he was a shell of himself.
“I think he threw 30 per cent of the punches that he threw in the first fight. He was finished, he was done, he didn’t even have the energy to fight back.”
Benn dominated the fight, dropping Eubank twice in the final round as Next Gen appeared sluggish and unable to generate his usual pace.
While Shalom insisted he did not want to make excuses, he strongly suggested Eubank Jr. was physically compromised.
He said: “Chris was not in the state he should have been to have a fight like that.”
Pressed on whether Eubank Jr. was carrying a medical issue into the bout, Shalom declined to elaborate.
He said: “That is for him to talk about. All I’ll say is that he knew, and we knew on the day that he was not right.”
Shalom also criticised the rehydration clause, arguing it endangers fighters and should be banned.
He said: “The clause in particular is something that shouldn’t exist in boxing … one day that could go wrong, and there will be people to answer for it.”
