Steve Agnew hoping to get Middlesbrough job full-time

Agnew, who took over the reins following Aitor Karanka’s departure on Thursday, said: “It is a club I have a great affection for, I love the people in the area and the passionate crowd of North East football.”

His first game in charge unsurprisingly ended in defeat.

Marouane Fellaini - his first in the league this season - and Jesse Lingard scored either side of half-time to put United in the driving seat until substitute Rudy Gestede pulled one back for Boro.

However, Victor Valdes’ late slip handed Antonio Valencia the simplest of chances to make it 3-1 and ease Mourinho’s men into fifth place in the table.

Agnew saw positives from his side.

“It is a pleasure to be in charge of a team and see a team respond like they did,” he said.

“I think the second goal is what set us back a little bit but in terms of the players, I couldn’t be more proud of the players, the fighting spirit they showed, the crowd was top-class.

“If we show that commitment and that sort of intensity until the end of the season then we have a real chance of staying in this league.

“It is a relief to get a goal and I felt that when we got that goal, we had Manchester United defending in the box for their lives and again we didn’t quite get the bounce of the ball to get the equaliser, which on the balance of play I thought we deserved.

“I know that in the coming games that we will take that fighting spirit for the rest of the season.

“The performance was intense, it was everything you want in terms of commitment. Of course we have got to start winning football matches, but I have been in this league before and I know that one game, one win, three points can change everything.”

The game was marred by an ugly melee after Rudy Gestede and defender Eric Bailly had clashed, and there was pushing and shoving in the tunnel after the final whistle.

Gestede insisted there was no bite from him or Bailly during the clash.

“We had a few words together, it was nothing major,” the Boro striker said. “He gave me a hug and a kiss, that’s it. I didn’t feel anything.

“Ben thought he bit me, so that’s why he reacted like he did. But I told him now we were just talking, there was no problem.”

The opener came when Ashley Young, deployed as left wing-back, cut onto his right foot and floated a cross to the far post for Fellaini to power in a header.

Lingard added the second with a stunning shot from 25 yards into the top corner.

But the game was not over as Alvaro Negredo, a handful all afternoon, directed two headers off-target as Boro pushed for a goal that arrived in the 77th minute.

January signing Gestede shot past De Gea after some woeful defending and Negredo was denied a penalty after going down under pressure from Phil Jones.

But Valdes’ slip in injury time allowed Valencia the simplest of tap-ins to finally kill off the home side.

Middlesbrough: Valdes, Barragan, Bernardo, Gibson, Da Silva, de Roon, Clayton, Leadbitter (Gestede 67), Downing, Negredo, Ramirez (Traore 68). Subs Not Used: Guzan, Stuani, Fry, Guedioura, Forshaw. Booked: Clayton. Goals: Gestede 77.

Man Utd: de Gea, Bailly, Smalling, Jones, Young, Carrick, Fellaini, Valencia, Mata (Rojo 69), Lingard (Martial 80), Rashford (Darmian 90). Subs Not Used: Romero, Mkhitaryan, Shaw, Fosu-Mensah. Booked: Jones. Goals: Fellaini 30, Lingard 62, Valencia 90.

Att: 32,689 Ref: Jon Moss (W Yorkshire).