Roy Keane warned Manchester United were taking a risk with Cristiano Ronaldo

It was never likely that Cristiano Ronaldo’s second spell at Manchester United would be a long one, although there looks to be an increasing danger of it becoming much shorter than the club and its fans had hoped.

With yet more reports emerging of a potential exit for the five-time Ballon d’Or winner this summer, the fear around Old Trafford grows. United’s failure to qualify for next season’s Champions League was always seen as having the potential of leading to Ronaldo’s exit, and the latest speculation suggests that could well be the case.

United remain adamant that the 37-year-old is not for sale, but if his last two moves have proven anything, it’s that Ronaldo will surely be the one to decide whether he stays or goes. United can’t say they haven’t had enough warning of that.

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There will be plenty of discussion over what effect Ronaldo’s exit would have on the side, but there can be no doubt about it leaving them in a rotten position up front. United legend Roy Keane said as much when outlining why the club need to keep hold of the Portugal international this summer.

"It was a short-term fix, for the fans, for the share price. But he has still scored the goals," Keane told Sky Sports back in May. "Manchester United have bigger problems than Cristiano Ronaldo.

"I just think with the goals that he has got, his performances, warrants staying at the club. But Manchester United have to get players around him, they have to get other strikers in, there has to be competition for places.

"If the leading goalscorer, the man you are depending on, is 37 years of age then that is certainly not good but I would certainly be holding onto Ronaldo.

"There