Rather than criticise his Championship players, the Italian preferred to compliment a City team apparently on the upgrade under their new manager Steve Cotterill.
It looked as though Watford would emerge victorious from a tough afternoon when Sean Murray fired them in front with a low right-footed drive that caught home goalkeeper Elliott Parish unsighted on 84 minutes.
But less than two minutes later Bristol substitute Wes Burns burst clear down the right and pulled back a perfect cross for Jay Emmanuel-Thomas to shoot home his 18th goal of the campaign.
Sannino had no complaints and he said: "We have to give credit to Bristol City for playing a very good game and I believe a draw was a fair result.
"It is a negative for us that we could not hold an advantage gained so late in the game, but these things happen in football and I have to congratulate Bristol because they deserved to equalise.
"I knew that this competition produces some strange results and I am told there have been some today, so we were prepared for a tough game.
"The main positive for me is that although we were without some players we stuck to our game and were patient. I know we can play better, but we are on a tough schedule of games and I am looking forward to a free week to work with the players."
Watford felt they were denied two penalties in the first half, the first when Diego Fabbrini went down under a challenge from behind by Liam Fontaine on 15 minutes. Referee Paul Tierney elected to neither point to the spot nor issue a caution for diving.
Five minutes before the break Gabriele Angella clipped the crossbar with a powerful header and also claimed he had been impeded when trying to reach the ball.
But the hosts had their chances too before the goals. Joe Bryan forced the best save of the game from Manuel Almunia in the first half and the Hornets goalkeeper also had to dive to keep out a second-half effort from Sam Baldock, while Karleigh Osborne headed over from a great opportunity.
Manager Steve Cotterill was understandably delighted, even though he had hoped to avoid a replay at Watford on Tuesday week.
"I threw on substitutes at the end to try and win the game because we wanted to do it at the first attempt, but I am pleased to be still in the FA Cup," he said.
"We have more than matched a good Championship side and if anything deserved to nick it at the end.
"It is a great effort by Jay to have 18 goals at this stage of the season, but I don't think he deserves all the headlines today because it was a really good team effort and I am happy with all my players.
"Wes Burns had the effect I wanted when he went on and I thought he might cause them problems. He is a young player I rate highly, but we need to be careful with him."