Michael Carrick’s Middlesbrough side leapfrogged Watford and moved up to third in the Championship table by winning the meeting of two play-off hopefuls.
That made it nine wins from 13 league games for Carrick, who took the manager’s job in October after Boro had slipped into the relegation places.
The Teessiders handed on-loan Aston Villa striker Cameron Archer a full debut, and he played a big part in the opening goal, eventually scored by Chuba Akpom, his 15th of the season.
With midfielder Dan Barlaser watching from the stands ahead of his imminent move from Rotherham, Boro forged ahead in the 36th minute when Archer’s pace took him clear of the Hornets defence.
His touch deserted him and afforded Watford keeper Daniel Bachmann the chance to block his shot, but the ball lobbed into the air and Akpom, despite slicing his attempted volley, was able to follow up and head into the empty net.
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Akpom was a constant threat and with Archer’s pace also causing problems for the visitors’ defence, the result was never in doubt.
Boro sealed the three points in first-half added time when Jonny Howson threaded a neat pass into the path of Marcus Forss, racing inside off the right wing.
He ran across the face of the defence and, with Bachmann advancing, reversed his shot into the corner.
Watford reacted by sending on Benfica loanee Henrique Araujo at half-time as a substitute, and he almost made an immediate impact as the Hornets had their best spell of the game but Zack Steffen raced off his line to block the Portuguese striker’s shot.
Defeat leaves Watford in fourth, with the rest of the Championship’s top half not in league action this weekend.
Middlesbrough boss Michael Carrick told BBC Radio Tees:
“Cam (Archer) was terrific, not really surprised by it after watching him training for the last couple of weeks. He gave their back line problems with his movement and sharpness, and by doing that created space for Chuba, Riley (McGree) and Marcus who all looked dangerous in different ways.
“There was a lot to be pleased about. It was a tough game going into it, with the attacking threat they have got.
“We got some chances from our press but as the game went on we played some terrific football. It gives us a bit of a boost and the confidence to believe we can do it.
“The boys got what they deserved. We had a number of chances but our play probably warranted an extra few chances but the final pass or decision shows there is still work to do.”
On Dan Barlaser: “It’s not totally tied up, there are a few little things to clear up but we are pretty close, which is obvious as he is here. He’s a terrific player, a good person and character.”
Watford boss Slaven Bilic told BBC Three Counties Radio:
“Basic things. I’m not talking about finishing, or crossing or decision-making in the final third, things you should normally be talking about.
“I’m talking about passing the ball to your player and not making those kinds of mistakes, and if you do that and slip so many times as we did, especially in the first half, and then on top of that you concede the first goal like that, there is no point talking about systems.
“There were too many errors. Every time we passed the ball well we were pinning them back but if you give the ball away so many times you have no chance whatsoever.
“The first goal came from our corner or free-kick, we were trying to clear the ball and the reaction of our player on the halfway lineâ¦ kick the ball out of the game when you know you are the last man. It’s hard to explain and is nothing to do with quality, to make that kind of decision is unacceptable.
On Araujo debut: “It was hard for him to come on when we were losing 2-0 but you could see after a couple of minutes the situations he likes, and how he knows how to get there with timing, movement and quality, and he is going to be a big benefit for us.
“It was planned that he and (Keinan) Davis would play 45 minutes each as Keinan is coming back from injury.”