Ralf Rangnick rages at handball rule as Middlesbrough stun Manchester United in FA Cup

Manchester United's interim manager Ralf Rangnick was left confused and "surprised" after Middlesbrough's equaliser in their FA Cup tie on Friday night was allowed to stand despite a handball in the build-up.

The goal proved decisive as Championship side Boro went on to stun their Premier League opponents in a dramatic penalty shootout and advance to the last 16 at Old Trafford.

Jadon Sancho had given the hosts the lead in the first half and United should have been out of sight, with Cristiano Ronaldo missing a penalty as well as other chances, while Bruno Fernandes and Marcus Rashford were also culpable.

Boro then took their chance in the 64th minute when Matt Crooks levelled, although the ball had clearly hit Duncan Watmore's arm before he played the ball across goal.

In a tense penalty shoot-out, the sides could not be separated until Anthony Elanga blazed the 16th kick over the crossbar to send Boro's fans wild.

While Rangnick lamented his side's profligacy, he was understandably miffed by Boro's equaliser.

"How can it be accidental if he controls the ball up in the air with his hand? It was clear it should not stand but in the end I was really surprised it stood," Rangnick said.

"We conceded a goal which I don't understand why it stood. He controlled it with his hand. In the moment when they scored, it was clear that VAR would not allow this goal to stand."

The ball hits Duncan Watmore's arm in the build-up to Middlesbrough's equalising goal against Manchester United. Getty Images

The handball rule was tweaked for this season and now states "if an attacking player's accidental handball immediately precedes another player scoring, the goal will now be awarded".

Even Boro manager Chris Wilder was surprised the goal