Blues' manager was reportedly shocked the club had to pay so much to release him from his Dragoes contract, but is sensitive to accusations of money-grabbing by Portuguese press
In what was a record buy-out of a manager’s contract, Villas-Boas was prised from Porto after one season in European football in which he won the treble.
However, Walsh has told The Daily Mirror that the young manager will justify the large payment and be a great success: "He did a great job at Porto last season by winning a treble – the Portuguese title and Cup as well as the Europa League.
“He thought Porto might have priced him out of the market and he was prepared to stay at Porto. There’s no doubt about that. That was clear in his mind.
“But all that changed when Pinto da Costa, the Porto president, revealed publicly the exact details of Andre’s contract."
Walsh explained: “Pinto da Costa’s a very shrewd guy. Remember, this is the guy who spotted Jose Mourinho’s potential, recruited Andre from a small club called Academica Coimbra and has now put in a new coach with an £18m get-out clause!
“It was actually €15m as compensation for Andre, an incredible amount. That’s why he thought no one would pay it. In fact, only one team in the world would do it and it was Roman Abramovich and Chelsea.”
Villas-Boas has been criticised in Portugal for taking Chelsea’s money after pledging his future to Porto, but Walsh is adamant that he did the right thing by moving to England.
Walsh said: “You can’t blame Andre for taking the Chelsea job – it might only have come to him once in his career.
“The media in Portugal may be on his case but the circumstances around his career changed dramatically.
“I’m sure deep down there’s a tinge of sadness within Andre at leaving his hometown club.”