The goalkeeper was in fine form as we came under pressure in the fourth round clash at Vicarage Road.
He produced top-drawer saves to tip Sean Murray's curler onto the post and then block Nyron Nosworthy from close range.
Michael Dawson and Kyle Walker also made key blocks and the Hornets hit the woodwork as we scrapped it out for a place in the fifth round.
In the end, Rafa van der Vaart's 30-yarder secured victory and we'll travel to Stevenage in the the last 16, date still to be confirmed.
"That is the story of the FA Cup," said Carlo.
"How many times have we seen an underdog beat the big team? We didn't play our best football but we came away with the result.
"The FA Cup has a different mentality, a different way of playing and we know that.
"It was more difficult than we thought, for sure. We didn't play well, they gave everything, pressed, created chances and we're quite pleased to go through this round.
"But you can't always win matches playing good football, especially when you come to somewhere like Watford, sometimes you have to win it ugly."