It was not the most usual moment for levity, but as Gavin Rees was entering his final moments as a world champion, he was able to see the funny side. Tired, battered, bruised and with swabs stuck up both nostrils to stem bleeding, Rees looked a sorry sight as Enzo Calzaghe, his trainer, tried to cajole a final effort from him before the twelfth round.

“You've got to get the big shots going - the big, big shots,” Calzaghe said. The WBA light-welterweight champion replied: “But I hit him with the big shots,” and burst out laughing.

Rees was heading for defeat against Andreas Kotelnik, at the Cardiff International Arena on Saturday, but was denied the satisfaction of hearing the final bell when the Ukrainian forced a stoppage with 26 seconds remaining, as Rees's stamina, which had been flagging during the last six rounds, finally gave out.

The 27-year-old Welshman had won the title last July in a big upset against Souleymane M'Baye. At 5ft 3in, he always seemed too small to be a light-welterweight, but given his chance, he boxed brilliantly and found the French champion in thoroughly compliant mood.

Kotelnik, the WBA's mandatory contender, was never likely to make the same mistake. He had won a silver medal in the Sydney Olympics - beaten in the final by Mario Kindelán, the Cuban who beat Amir Khan in Athens four years later - lost a narrow decision to Junior Witter, now WBC champion, for the European title three years ago and had drawn against M'Baye last year. He used his size advantage well and weathered Rees's early onslaught, never let his tight defence slip and found the Welshman with the straighter, harder punches.

“He was catching me with some big shots,” Rees said. “In around the fourth round, he caught me on the ear and it really hurt. It was like ‘wallop', and it seemed to sap all my energy. He was a heavy hitter, it was a struggle from then on.”

While Rees stayed in contention during the first half of the bout, the body shots he landed - the only thing he had much success with - had little effect. He seemed to get increasingly frustrated and was often caught with his gloves down in Kotelnik's range.

During the later rounds he seemed to be boxing in the verge of exhaustion, summoning all his energies into a huge effort in the first 90 seconds of each round before flagging. In the final round, Rees seemed to ignore defence and paid for it when Kotelnik landed two big rights, which had him reeling, and he fell to the floor as he tried to hold. Although it was not ruled a knockdown, Luis Pabón, the Puerto Rican referee, stopped the bout moments later to save him from Kotelnik's next onslaught.

It was another blow for Calzaghe's camp. Having not trained a loser in more than three years, he has now lost two of his three world champions within a fortnight, after Enzo Maccarinelli was beaten by David Haye, not the greatest of omens ahead of son Joe's bout with Bernard Hopkins in Las Vegas next month.

While Rees joked that he would probably spend the next week “in the pub”, he acknowledged that his future lay in a lighter division, where a bout against Amir Khan could happen later this year. “Lightweight is probably my best weight,” Rees said. “But I got a shot at the title and won it, so obviously I was going to defend it.

“I'm proud to have been a world champion, every boxer would be. Hopefully I can be world champion again. This is maybe a blip in my career. You've got to laugh or you cry and I know which one I prefer to do.”

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