Roy Keane says he regrets moving to Celtic and believes he should have retired the day he left Manchester United.

The legendary Irishman was effectively booted out of Old Trafford in November 2005 after savaging the team’s performance in their 4-1 defeat to Middlesbrough on MUTV. The interview never aired, but Sir Alex Ferguson caught wind of his skipper’s comments and sent him packing.

A month later Keane signed for Celtic, though he only managed 13 forgetful appearance for the Scottish club before hanging up his boots at the end of the season. Speaking this week on the Stick to Football podcast, brought to you by Sky Bet, Keane admitted his Celtic Park switch was a mistake.

“I was 34 when I finished [playing football]. I should have retired when I left Manchester United, the day I left the club,” he said. “I even lost a bit of the love for the game after that, I left Manchester United and went up to Celtic, my hip was at me, painkillers for training, tore my hamstring two or three times, commuting, thinking I’m 34 now.

“I still had a year left on my contract [at Celtic] and I went to see the hip specialist and they said that the longer I play the worse damage. The beauty is that when I rang Gordon Strachan, I told him that I’m finished, I was losing sleep before I rang him but as soon as I put the phone down I had closure on my career, no hesitation, it wasn’t a relief but something was lifted off me.”

Keane spent 12 years in United’s first team, but tensions between him and Ferguson began to rise in the summer of 2005. The two came to verbal blows in a dispute over the quality of the facilities at their pre-season camp in Portugal, and Keane poked the bear even further after admitting to MUTV that he was “prepared to play elsewhere” a few weeks later.

His controversial interview after the Middlesbrough defeat then severed whatever was left of his deteriorating relationship with Fergie. In it, he not only slammed the team’s performance but also singled out several individuals like Rio Ferdinand, John O’Shea and Darren Fletcher. On Ferdinand, who was the club’s record signing at the time, he said: “Just because you are paid £120,000-a-week and play well for 20 minutes against Tottenham, you think you are a superstar.”

The outburst was immediately deemed too volatile for publication by MUTV bosses, who described Keane’s comments as “explosive even by his standards”. A couple of weeks later, Keane and Ferguson butted heads again and the pair mutually agreed to terminate Keane’s contract.

In 2019, the former midfielder claimed the club were intentionally pushing him out the door due to his age and the fact he had a strained relationship with Ferguson’s assistant Carlos Queiroz.