Former Manchester City assistant coach Mark Bowen says Robinho was up to competing in the Premiership.
Robinho, 26, arrived at Eastlands for a record British transfer fee of £32.4m in 2008 but faded after a bright start.
"He took a lot of stick, but he did massively underperform, especially away from home," said Bowen.
"I just thought that, physically, he wasn't really up to the challenges of the Premier League."
Robinho left Manchester City in January, rejoining his first club Santos on loan for six months, and Bowen, who left Eastlands along with sacked former manager Mark Hughes in December, believes he will prosper in a more familiar environment.
"There is no doubting that if and when he went to another league, or back to Brazil, it would be a different style of football and it would suit him better," said Bowen.
"We always felt he could possibly blossom and get used to the Premier League but he wasn't really up to the week in week out challenges."