Diao, who finished last season as a Stoke player after leaving Liverpool, penned an 18-month deal at the Britannia Stadium on Monday to finally end speculation over his future.
The 30-year-old's move to the Potteries never materialised over the summer and there were fears he may have been lining up a move back to the Premier League.
However, Diao told The Sentinel he was recovering from a knee injury and insists there was never any doubt in his mind he would return to City.
He said: "There was quite a bit of interest in me - including from Premier League sides - but none more so than Stoke, and that kept me going.
"My dream is to get back into the Premier League with Stoke, and if I didn't think that was possible I wouldn't have come back."