The Italian called on Barry to replace winger Adam Johnson after the Premier League side went a goal down at the Etihad Stadium.
After the switch, City managed to draw level at then go on to beat the Spanish side 2-1 on home turf.
"It worked straight away really with the goal coming just before half-time, it was strange coming on for someone as attacking as Adam Johnson but Yaya Toure pushed forward and caused Villarreal problems," talkSPORT quotes Barry as saying.
The midfielder concedes that the competition will be "tough" as they continue to face Europe's elite.
"The whole club and the players are adapting to the Champions League," he added.
"It's my first taste of the Champions League and it is a step up, it's a real tough game every time you step out there and there are quality players everywhere."
Meanwhile, the North West side turn their attention back to the Premier League as they prepare to face rivals Manchester United on Sunday.