The Gunners were competing with Manchester United to land Ronaldo from Sporting in 2003, while earlier this season Arsene Wenger admitted his “biggest regret” was missing out on the Portugal international.
In a new biography that will be released in English this year, titled ‘The Agent One’, Mendes concedes that Arsenal were very close to signing the three-time Ballon d'Or winner before a lack of financial power scuppered the deal.
“There was a moment in which I really thought he was going to Arsenal,” said Mendes.
“David Dein [Arsenal’s former vice-chairman] is a spectacular person but, with the construction of their stadium, they were left with very little money and it wasn’t possible.”
Mendes also revealed that Sir Alex Ferguson’s desire to immediately use Ronaldo in United’s first team was the tipping point in negotiations.
“The only person key to everything was Alex Ferguson,” he added.
“He told me that Cristiano was going to play at least 50 per cent of the games for Manchester United and that’s what I wanted to hear. That’s why Cristiano went to Manchester United.”