At the start of the season, Pep Guardiola allowed the young full-back to spend the campaign at the newly-promoted La Liga side and Maffeo has gone on to make 20 appearances in Spain's top flight.
However, in his first spell at the club in the first six months of 2016, Maffeo barely featured and the youngster has admitted that he needed to endure frustration before he could continue to 'mature' both on and off the pitch.
The 20-year-old told the Daily Mail: "Loans mature you as a professional. It's where you get used to playing week in week out, it's also where I've learned to deal with not playing and having a bad time when you are out the team and in that way learning what football can be like.
"It's worked out well for me this season but when I came here the first time I didn't play much. It toughens you up and make you grow up. This if professional football and you are not going to play just because you have come from Manchester City."
Maffeo has been contracted to City since 2013, making three appearances in cup competitions.