You may have missed Casemiro being 'sent back to Madrid' on first Man Utd start by outrageous skill

Manchester United superstar Casemiro was completely dumbfounded by a piece of skill from Real Sociedad left-back Aihen Munoz on Thursday evening.

United slipped to a 1-0 defeat in their opening Europa League Group E clash thanks to a controversial Brais Mendez penalty just before the hour mark.

Casemiro made his first start for the club after a £60 million transfer from Real Madrid in the summer, alongside Christian Eriksen and Fred in central midfield.

The Brazil international was left in the dust by Munoz, who pulled off a filthy back-heel nutmeg by the touchline. Give it a watch below.

Footage of the incident went viral on social media and rival fans were quick to mock Casemiro, who is one of the most decorated players of the modern era.

One person said: "Luka Modric said 'It’s all downfall after Real Madrid' and he was absolutely spot on."

Another added: "Their best DM being ridiculed in the Europa League."

A third tweeted: "I'm gonna have to pretend I didn't see this."

While someone put: "Has he ended Casemiro's United career before it even started?"

United fielded a much-changed XI from last weekend's 3-1 victory over Arsenal and it was a cagey affair at Old Trafford.

Midway through the second half, La Real were awarded a penalty after Lisandro Martinez was judged to have handled in the box.

Replays showed the ball bounce off the defender's leg and onto his arm, but referee Marco Di Bello's decision stood with no VAR intervention.

Mendez stepped up to convert his spot kick with ease and give the away side their first-ever victory over United.

Cristiano Ronaldo started up front and his hunt for a first goal this campaign goes on. He thought he'd opened the scoring in the first half, but the five-time Ballon d'Or winner was correctly ruled offside.

United were set to face Crystal Palace on Sunday but that game has been postponed, along with nine other Premier League fixtures this weekend, following the death of Queen Elizabeth II.