Manchester United were humbled at Watford last season - and Jose Mourinho is expecting an even tougher test at Vicarage Road this time around.
Late goals from Juan Zuniga and Troy Deeney gave the Hornets a 3-1 victory in September 2016, condemning the Red Devils to their third defeat in a week.
That period remains the lowest ebb of Mourinho's Old Trafford reign and the United boss is aware just how hard it will be to exact revenge on Tuesday evening.
Watford are eighth in the Premier League after their impressive 3-0 win at Newcastle, with manager Marco Silva's fine work leading to admiring glances from rudderless Everton.
"Against Watford I was very upset with Watford's first goal after some guy sent (Anthony) Martial to the hospital and the referee let it go," Mourinho said.
"That is the reason why I was very, very upset at Watford. I think Watford made also progress.
"They have an unusual squad for a mid-table team.
"They have a squad full of very good players who are not normal to be in these mid-table teams. They have a good coach.
"They have improved a lot from last season too."
Mourinho failed to get the better of Silva in their last two meetings, with his Hull side holding United to a goalless draw in the league at Old Trafford just a week after beating them 2-1 in the EFL Cup semi-finals in January - albeit a scoreline that did not prevent the Old Trafford giants from progressing.
Zlatan Ibrahimovic starred as the Red Devils went onto triumph at Wembley and is now pushing for his first start since April, having made three substitute appearances after returning from serious knee ligament damage.
Marcos Rojo has started the last two matches after being sidelined by a knee issue of his own, although should Phil Jones or Eric Bailly return from injury the Argentina international could be protected.
How best to utilise Paul Pogba is another question for Mourinho given the trip to Watford is swiftly followed by a trip to Arsenal on Saturday.
The 24-year-old has impressed since returning from a hamstring complaint, completing his first full match in 11 weeks against Brighton.
"I think (United will improve as he improves)," Mourinho said of Pogba after Saturday's 1-0 win.
"He was on the pitch and I think Paul played very well but even with Paul on the pitch I don't think we managed to be fully in control.
"They had three players in midfield, normally they have two. Pogba and (Nemanja) Matic it was difficult for them to press.
"Marcus (Rashford) and (Anthony) Martial are without the tactical knowledge that an older player has to close the spaces between the full back and the number six.
"Even with Paul, we were a little bit in trouble, but Paul played very well against Basel and very well again (against Brighton).
"I wanted to take him out but I felt the points were still there to fight for.
"And I knew in the last part of the game they would bring (Shane) Duffy up and play long balls so I thought (Marouane) Fellaini would be important but Paul was as well.
"Paul was one of the guys who kept possession well, brought the ball into the corners, trying to win a few seconds of possession away from our goal, so Paul was good."