Guardiola has praised Alvarez for grabbing his chance amid injuries to several of his attacking players.
Ahead of facing Nottingham Forest, Guardiola said: "Always have good behaviour, playing, not playing, being a world champion or not.
"Always the same.
"The perfect dose of disappointment when he doesn't play but always ready for the opportunity. Last season we had Ilkay [Gundogan] and Kevin [De Bruyne]. Right now with the injuries he's had minutes and he gives us a lot of good things.
"That's why he's playing but he has to continue. Many games, some games he won't play, hopefully, players come back and fight for positions."