Goals either side of the break by substitute Darius Henderson put Watford on course for a fourth straight win before the Blades hit back.
Phil Jagielka headed the first shortly before Paul Ifill's shot was deflected in to make it 2-2.
Malky Mackay saw red before Carlisle deflected in Nick Montgomery's header.
Sheff Utd manager Neil Warnock:
"I thought it was a super advert for the Championship.
"It was a sending off. He (Malky Mackay) backheeled him (Rob Kozluk). After that they lost a little bit of discipline.
"The ref was a little bit lenient but they have such difficult jobs."
Watford: Foster, Doyley, Carlisle, Mackay, Stewart, Devlin (Blizzard 74), Spring, Fletcher, McNamee (Chambers 58), King (Henderson 17), Young.
Subs Not Used: Chamberlain, Bangura.
Sent Off: Mackay (67).
Booked: Henderson, Carlisle.
Goals: Henderson 39, 53.
Sheff Utd: Kenny, Kozluk, Bromby, Morgan, Unsworth, Ifill, Jagielka, Montgomery, Alan Quinn (Gillespie 77), Shipperley (Webber 56), Kabba (Nalis 90).
Subs Not Used: Tonge, Geary.
Booked: Kozluk, Bromby.
Goals: Jagielka 56, Ifill 66, Carlisle 81 og.
Ref: M Clattenburg (Co Durham).