Boosted by last weekend's stunning comeback victory at West Ham, Walter Mazzarri's side, who have used 22 players already this term, are looking to end a disappointing run of three consecutive home defeats in all competitions and register their first win over the 20-time champions for 30 years.
Seasoned centre-back Kaboul, who joined Watford from Sunderland last month after asking to leave Wearside for personal reasons, started back-to-back fixtures either side of the recent international break, but picked up a knock with just eight minutes remaining at London Stadium and was replaced by Austrian international Prödl.
Now both players face late fitness tests to determine their status for the visit of José Mourinho's United, who followed their Manchester derby defeat with an insipid 1-0 Europa League Group A loss to Feyenoord in Rotterdam on Thursday (15 September).
"I need to verify today and tomorrow Kaboul's condition and also Prödl had a problem during the week," former Napoli and Inter Milan head coach Mazzarri, appointed as successor to Quique Sanchez Flores in May, was quoted as saying at his pre-match press conference by the Watford Observer.
The likes of Nordin Amrabat, Christian Kabasele, Chelsea loanee Kenedy and Jerome Sinclair will all be bidding to return to the Hornets' matchday squad after being left out against West Ham, but Stefano Okaka faces the possibility of an extended spell on the sidelines.
The Italian striker, another new arrival having been signed from Anderlecht on a five-year deal in August, made his Watford debut as a late second-half replacement for captain Troy Deeney last week and his lively short cameo included a yellow card for dissent and a goal that was disallowed for offside. He later limped off before the full-time whistle due to an apparent hamstring problem.
"Okaka also won't be available," the manager, keen to play down his heated rivalry with Mourinho dating back to their respective spells in Serie A but risking ridicule by insisting that he would opt for Roberto Pereyra over Paul Pogba, added. "At the moment this is the situation so I need to verify it at the last minute."