The midfielder struck a late equaliser for the hosts.
Guardiola said, "It was a tight game like we expected, they defend solid, had 10 players in the box.
"It's one of those days, they defend so deep, we play so good.
"Maybe in the first half we should move more left-right-right-left, but we create enough chances. We conceded two short on target and concede two goals. The way we played was really good, we created chances and 10 players in the box is not easy, [Martin] Dubravka made good saves.
"At the end we shouldn't concede the free-kick and Shelvey made the difference.
"Shelvey put it in the corner, [but] we could have avoided it in that position."