The English champions were kept at bay by Chris Wilder’s men for a large portion of the game despite mounting numerous chances.
Dean Henderson kept the hosts in the game with breathtaking saves which included denying Gabriel Jesus from the penalty spot.
The visitors got their breakthrough when substitute Sergio Aguero tucked in from close range from Kevin De Bruyne's teasing low cross into the six-yard box.
Guardiola insists Bramall Lane is a difficult place to visit and labeled Henderson’s saves as incredible.
"We knew it would be a difficult place to come,” the former Barcelona and Bayern Munich manager said.
“We concede one or two clear chances, nothing more than that.”
“In the first half the keeper was excellent with the penalty and two incredible saves, it was an incredibly good victory for us to take a step towards securing Champions League football next season.”
"In the first half we were a little bit shy to play, but in the second half we were a little bit more like we are. But we controlled it really well, the chance to score goals.”
"What Sheffield United do, they do it perfectly. They’ve been together for five years so their spirit is so good. They are so good at the second balls and arrive with a lot of people in the final third."
