For the second season running the Blues edged out Leicester in a fifth round penalty shoot-out after the sides had been locked at 1-1 after 90 minutes.
The victory kept the Blues on track to defend the Carabao Cup we won last year.
And after making eight changes to his starting line-up from the side that beat Everton at the weekend and handing a full debut to 17-year-old defender Eric Garcia, Guardiola was full of praise for his players.
"It was a tough game but that is normal - it is always difficult at Leicester,” said the boss.
“We made quite a good performance. Of course, we had chances to win the game before.
“It was the same last season when we won with penalties thanks to Claudio (Bravo). This year it was Aro.
"Raheem took that decision [to chip his penalty], unfortunately he missed it but that is OK."