The Algerian netted City's second goal to secure all three points after Kevin De Bruyne's deflected effort restored parity following N'Golo Kante's opener.
Picking the ball up on the right wing, Mahrez jinxed in between two defenders and curled a powerful effort into the far corner.
It was a fantastic goal,” said Guardiola afterwards.
“I’m willing the best for my players and Riyad. The quality is there, but he can do better. We’ve seen this season his top quality and he made a fantastic goal today.
"He fought a lot and I’m pretty sure we’re going to see an increase in the next weeks.”
Hear what else the boss had to say following the victory by watching the video above.