With his side leading 20-12 against the 12-men visitors, the Airlie Birds prop was red-carded for a head-butt in the 72 minute, an offence which is sure to see him banned at tomorrow’s RFL disciplinary.
Hull had been 18-0 ahead on Friday but conceded back-to-back tries after Declan Patton was dismissed to leave head coach Lee Radford ‘panicking’.
Washbrook – who switched from back-row to start at hooker–- said: “Warrington did get roused when a man down.
“We’ve done the same in previous games when we’ve gone down to 12 men.
“It does give you a sort of added extra energy as you know you have to work that little bit harder out on the field.
“We knew that would come from them and it did. We felt in control for most of the game but they’re a quality team so if you give them a sniff they’ll come back into it which they did.
“I was a bit frustrated sat on the bench so I can imagine the boys would have been feeling it out there but we managed to hold on and show a bit of resilience to get the points.
“I say hold on but if Wattsy hadn’t got sent off we might have won it more comfortably,” he added.
It was Hull’s first win in four games but they must improve at champions Leeds Rhinos on Thursday.
“The few games hadn’t gone our way so to get the W,” said the ex-Wakefield Trinity forward. “That was the all-important thing and we managed to do that so we roll onto Leeds now next week.
“It will be really tough going to Headingley. It always is there. Radders reminded us we haven’t won there for about 12 years so we know what type of challenge it is.
“They are a champion team so we need to be on our guard,” he added.
Friday’s game was played in atrocious conditions.
Washbrook, 32, said: “It was freezing when we came out for kick-off and then again coming out for the second half but in between you’re alright.
“Apart from when sat on the bench...it was cold!”