German Eduard Gutknecht was taken to hospital after Britain’s George Groves defended his WBA International super-middleweight title in London.
The 34-year-old fell ill in his changing room and was carried out on a stretcher and taken to hospital.
Gutknecht is in a stable condition and will continue to be monitored after having surgery and being sedated, the British Boxing Board of Control said.
Groves scored a unanimous points win in the fight at Wembley’s SSE Arena.
It moves him closer to a shot at the vacant WBA super-middleweight title.
The Londoner said he was “deeply concerned” for his opponent in a social media post on Saturday morning.
“Out of respect to Eduard Gutknecht and his family’s privacy, I don’t want to say too much but we are all deeply concerned to hear that he was taken to hospital after the fight last night,” he said.
“I sincerely hope it is nothing too serious and I would like to send out all my support and best wishes to him and his family at this difficult time.”
The judges awarded the fight to Groves, 28, with one scoring it 119-110 in his favour and two 119-109.
Groves has now won his past four fights since losing two world title bouts – one to Carl Froch and one against Badou Jack.
“I am very happy with how I fought – it went exactly to plan,” Groves told Channel 5 before news emerged of Gutknecht being taken to hospital. “I set a great tempo and busted him up badly. I am surprised he made it to the bell – Gutknecht is a tough character.
“We want real, big, proper fights. There was no world title on the line, but we knew Gutknecht was going to give me a tough fight. It will push me on for a world title fight and, ideally, I would love a rematch with Badou Jack.”
The Londoner looked confident against Gutknecht and hurt his opponent with a couple of blows to the head in the fourth round.
He continued to find the target with his combinations and cut open Gutknecht’s right eye in the 10th, but the 34-year-old managed to make it through the full 12 rounds.
Meanwhile, Welshman Andrew Selby stopped Jake Bornea of the Philippines in the seventh round in London.
Selby, the brother of IBF featherweight champion Lee, has now won all seven of his fights since turning professional in September 2015.
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