Riesgo left Eibar this summer and emerged as a surprise target for City, though the deal eventually failed to materialised as the Blues already had too many foreign players in their squad, with the limit being 17.
It's reported that Riesgo considered retiring after the failed transfer but instead Catalonian side Girona snapped him up on deadline day.
"The opportunity came from City and I was practically thinking I was going there," the Spaniard said.
"It collapsed and, in the end, it has been a very long summer.
"It was not an easy situation. I had a long summer and when I thought everything would work out, destiny took a turn. Now I am happy to take advantage of this beautiful challenge [at Girona] on a personal and sports level."