The Turkish champions were leading the 17th-placed hosts with five minutes to go but a late equaliser from Cameroonian Leonard Kweuke condemned Mancini's men to a draw, leaving them six points behind league-leaders Fenerbahce.
Gala have now won just one game in 2014, having drawn four of their five, including their Champions League clash with Chelsea.
And how cruel for the Italian that the club that parted company with him last season had landed their very first trophy since his departure on the very same day.
Mancini has already reportedly expressed his desire to leave Turkey at the end of season and this Sunday gone in particular might have been a day to forget for the 49-year-old.
Back in England, goals from Yaya Toure, Samir Nasri and Jesus Navas gave Man City a 3-1 win over Sunderland in the final of a tournament Mancini could never win during his time at the club.
His successor Manuel Pellegrini, meanwhile, is still on course for an unprecedented quadruple at the Etihad Stadium - or a domestic treble should Barcelona knock them out of the Champions League.
"To win the first trophy is important for us all. For the players, for me and for the staff," Pellegrini said after the Capital One Cup win.
"We are the only club with the chance to try to win all the competitions. We are going to try although we know it is not easy."
But it is European football that might give former City boss Mancini his only salvation this season, with Galatasaray still in with a chance of beating Chelsea in the last-16.
If not, however, the 49-year-old might be facing the ugly truth that his ex is much better off without him.
image: © Mafue