The Brazil international took the opportunity to impress in European competition, scoring the third goal against Shakhtar.
“He was involved and maybe involved tomorrow but it's difficult to find in Europe a player like Gabriel and how important he is," said Guardiola.
“His behaviour in training is outstanding, he has to fight for his place against a legend in Aguero.
“Sergio didn't play in the last game and he scored in all of the other games and Sergio fights for the team, that's why I'm so delighted with the striker.
“Gabriel, be patient I know when he plays he does absolutely everything like he has done in Ukraine, not just for the goal the way he fights and his future at this club is incredible."