The Dutch star spoke in the build-up to the match about how much he would love to play in the FA Cup Final at Wembley and it was his first half goal that saw us scrape into round five after a huge test at Vicarage Road.
Harry Redknapp and the players admitted afterwards that we were somewhat fortunate to come away with the narrowest of 1-0 wins.
The home side carved out a number of chances and will wonder how they failed to secure a replay at White Hart Lane.
The main reason why was goalkeeper Carlo Cudicini.
Always outstanding when called upon - his performance at Rubin Kazan in the Europa League remains one of the best individual displays this season - Carlo produced a couple of key saves as we held onto that slender lead.
The pick of the bunch was the slightest of touches to deflect Sean Murray's effort onto the post in the 50th minute.
Carlo was also in the right place to keep out Nyron Nosworthy's point-blank effort with 11 minutes left and Kyle Walker threw himself in to block Marvin Sordell's follow-up.
Harry made five changes to Sunday's starting line-up at City with Michael Dawson back in for Ledley King and captaining the team. He was joined by Cudicini, Danny Rose, Jake Livermore and Emmanuel Adebayor. Gareth Bale missed out through injury.
Watford started brightly and Cudicini was quickly into the action with comfortable saves from Sordell and Murray inside the first 10 minutes.
Prince Buaben drilled a yard wide from distance and Joe Garner failed to connect with Troy Deeney's cross.
We found our feet towards the end of the half and Jermain Defoe aimed a difficult volley straight at Scott Loach, our first effort on goal on the half-hour.
The key moment arrived in the 42nd minute. Watford were on the attack but play broke down and Walker sped out of defence.
He reached half-way and threaded a pass to van der Vaart 35 yards from goal. In space and central, van der Vaart took a couple of strides and opted to let fly, his shot zipping off the surface past Loach and into the corner.
Lennon entered the fray for Luka Modric at half-time but the second half followed a similar pattern, with the home side quickly back on top.
John Eustace fired just over from Murray's corner in the 49th minute and from the goal-kick, we lost possession, Garner found Murray and his curler looked set for the bottom corner before Cudicini touched it onto the post. Deeney followed in but could only side-foot wide.
Our best spell of the second half followed as Walker forced Loach to tip over a looping header and van der Vaart rattled the crossbar from 16 yards.
The home side hit back again though. Eustace struck the post when Cudicini appeared blocked from Yeates' corner and then Eustace could only glance a free header wide.
Cudicini's feet, Walker's legs and Dawson's head kept out Nosworthy, Sordell and Yeates respectively, with Yeates' effort the final serious scare eight minutes from time.
It was tough on Watford, and we'll settle for being in the fifth round draw on Sunday.
Watford (4-4-2): Loach; Hodson, Nosworthy, Mariappa, Doyley; Deeney, Eustace, Buaben, Murray (Yeates, 68); Garner (Whichelow, 80), Sordell. Unused subs: Bond, Dickinson, Iwelumo, Forsyth, Jenkins.
Spurs (4-3-1-2): Cudicini; Walker, Dawson, Kaboul, Rose; Livermore, Parker, Modric (Lennon, 46); Van der Vaart; Adebayor (Pavlyuchenko, 90), Defoe (Pienaar, 80). Unused subs: Friedel, Assou-Ekotto, Bassong, Kranjcar.
Goal: Spurs - van der Vaart (42).
Referee: Mr C Foy.