Jose Mourinho hailed Marouane Fellaini as 10-man Manchester United's main weapon in denying Watford a fifth successive Premier League win.
Fellaini was involved in both of United's goals from set pieces at Vicarage Road and repeatedly tracked back to help centre backs Chris Smalling and Victor Lindelof.
The 30-year-old midfielder, who has divided opinion during his time at United, was pivotal in this performance and Mourinho wanted to point out his talent afterwards.
'We made defensive mistakes against Brighton and Tottenham,' the United manager said. 'Against Brighton, we didn't deserve to win.
'Then we go to two difficult matches, difficult stadiums, Burnley and Watford, and I thought my central defenders needed somebody to support them and give them the first wall of physicality.
'But Marouane gives us more than that. He gives us quality and simplicity. He is playing simple and well. I am really happy for Marouane.
'I am very happy. With the points, with the spirit. I feel a bit frustrated because we had everything in the first half to kill the game.'
Mourinho's United have been practising set-pieces and the sight of two leading to goals particularly pleased the Portuguese boss. Romelu Lukaku scored their first before Chris Smalling got the second.
Smalling turned out with his hair twisted into knots and scored what proved to be the winner for Manchester United with a volley from close range in the first half at Vicarage Road.
'We trained the corner and it's the best thing that can happen to coaches when you train and see it happen in the match,' Mourinho said.
'They are happening in last three matches, even against Tottenham. Things we are working on, position and movement. The set pieces are a very specific thing. You work and work and for weeks you don't see the result so when it happened it was happiness for coaches.
'The only thing I don't like at this moment with Chris is the haircut but I am no one to tell him that.'
Smalling controlled the ball on his chest, held off a challenge from Daryl Janmaat and converted his first goal since April with style.
'You always hope they fall to you like that,' said the 28-year-old United defender. 'On my left foot, it was a nice one.
'When you're on top and 2-0 up there's always danger if they get that goal. It was a battle and we had to dig in.'
David de Gea also produced a stellar save in stoppage time to deny Watford an equaliser.
Mourinho added: 'Only one save but fantastic save. We know what it is to be the goalkeeper for a big team. Some matches you don't touch the ball and sometimes watching the game and in the right moment you have to be there.'
Watford boss Javi Gracia, who saw his side suffer their first loss of the season, said: 'Deserve or not, I don't know. We could do it in the last minute. A draw would have been a very good result. We tried.'