José Mourinho refused to answer questions about an unseemly altercation in the tunnel at the Riverside following a bad-tempered end to Manchester United’s 3-1 win at Middlesbrough.

Stewards were called to separate the warring players as a spat between Middlesbrough’s Rudy Gestede and United’s Eric Bailly continued beyond the final whistle with a bout of push and shove.

A suddenly silent Mourinho walked out of his post‑match press conference when asked about it.

Steve Agnew, Middlesbrough’s interim manager, was more forthcoming but, perhaps conveniently, claimed to have seen and heard nothing of the fallout after the Middlesbrough striker whispered something in his marker’s ear, briefly giving rise to erroneous suggestions he had bitten Bailly.

Agnew has succeeded the sacked Aitor Karanka, a close friend of Mourinho’s who assisted him at Real Madrid, and he suffered the indignity of the Portuguese neglecting to shake his hand at the final whistle. That finally took place when Agnew caught up with the United manager in the tunnel.

Mourinho also appeared to exchange harsh words with Stewart Downing, a player inextricably linked to Karanka’s exit, during the game but the United manager subsequently denied speaking to the former England winger.

A win secured with goals from Marouane Fellaini, Jesse Lingard and Antonio Valencia lifted United to fifth while Gestede scored a much-improved Boro’s first goal in five games and more than eight hours of Premier League football.

“A big win,” Mourinho said. “It was very important in keeping us alive in the fourth-position race. I would prefer to win the Europa League than finish in the top four because it would give us prestige, a trophy and Champions League football but maybe we can do both. Today was a massive victory for us.”

Agnew was encouraged by a performance in which Boro briefly threatened to force a draw.

“I’m not a particularly good loser but to push Manchester United all the way gives me optimism for the future,” he said. “Our attitude and application was first-class.” Agnew felt sufficiently confident to be convinced his charges were not to blame for the tunnel fracas.

“I’ve got a group of very well-behaved players,” said Agnew, who seemed unconcerned by Mourinho’s breach of touchline handshake etiquette. “I didn’t see anything, obviously something happened in the tunnel but it’s no concern to me.”

Agnew is more worried about Boro’s next three games – against Swansea City, Hull City and Burnley – and conceded he had “not really” had a conversation with Steve Gibson, Middlesbrough’s owner, to confirm he would be remaining in interim charge until the end of the season.

All the available indications though are that Gibson is minded to keep faith with a caretaker who “absolutely” wants the chance to lift Boro from their current 19th place to safety. “We have got to start winning,” said Agnew. “But I know that one game, one win, three points can change everything for us.”

Mourinho is similarly convinced a goal would alter Marcus Rashford’s horizon after a game in which the young England striker - who replaced the suspended Zlatan Ibrahimovic - showed off exemplary, and dazzling, movement only to be let down by sub-standard finishing.

He has not scored in the League since September and Mourinho acknowledged but played down the problem. “Rashford is in trouble to score a goal,” he said. “It’s really difficult to score a goal for him, but his movement is top class, his dynamic is second to none. He’s so intelligent, so sharp. For me, he played phenomenally. Goals will arrive, no problem at all.”