Ralf Rangnick blamed Manchester United for their 8-7 penalty defeat to Middlesbrough, the interim manager saying that being knocked out of the FA Cup was “our own fault”.

The fourth-round loss at Old Trafford all but ends United’s hopes of ending a five-year trophy drought as Rangnick’s misfiring team are outsiders for the Champions League and 19 points behind Manchester City in the Premier League.

While Anthony Elanga missed the crucial spot-kick, Rangnick contended that Matt Crooks’s second half equaliser should not have stood after Duncan Watmore’s handball in the lead-up to the goal was adjudged accidental by Anthony Taylor and VAR. “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,” said Rangnick.

Watmore said: “If I’m honest, it was completely accidental. I know it touched my hand but it wasn’t intentional at all. I was hoping it wouldn’t be handball and wasn’t expecting it but I haven’t seen it back and it doesn’t feel like it at the time.”

Rangnick was clear, though, that United were culpable for the loss. “In the first half we should have easily been 3-0 up and second half we had chances too. We should have won the game in normal time. On penalties it can happen what happened today,” he said. “We have to take our chances better and with more quality than we did today. It was our own fault – we should not have gone into extra time and penalties. For example, Bruno [Fernandes] chance [near the end] – if he has 10 of these in a match he scores nine.

“Today he hit the post, tried to place it too exactly – these things can happen, obviously he didn’t do that on purpose.”

Middlesbrough’s manager, Chris Wilder, said: “The FA Cup is alive and kicking – I told the players it was all about making memories. We rode our luck and took our chances. I thought straight away it was handball – I thought it would be chalked out and delighted it wasn’t.”