Corner kicks are undoubtedly one of the most under-appreciated skills in football.

They may be simple in theory, but every once in a while a player reminds us that some genuine magic can be produced from the flag.

Back in August 2016, for example, Santi Cazorla went to take a corner against Watford with his right foot but ended up using his left foot instead.

And the reason? Because Laurent Koscielny said so.

Koscielny was once of those waiting in the box for Cazorla's delivery and shouted to the Spaniard to swing the ball in with his left boot, rather than his right.

Arsenal didn't score from the set piece, but what Cazorla did had never been seen before. He's two-footed, after all.

And just the other week, Neymar set up Paris Saint-Germain teammate Layvin Kurzawa with a driven corner that found its mark with unerring accuracy.

Neymar spotted the run and leathered the ball into the box for Kurzawa to volley home. It's no exaggeration that very few players can pull off such a skill.

There have been various other examples of clever corner kicks down the years, but it's the Manchester United side of 2008/09 who take the crown.

During a 3-0 win over Chelsea at Old Trafford on Sunday 11 January, 2009, United produced a genius corner kick that completely fooled everyone - even the referee.

In the video below at 46:00, Wayne Rooney dribbles the ball to the corner flag and then leaves it for Ryan Giggs to take.

But what no one noticed was Rooney tapping the ball to effectively make it 'live'. Giggs then turns, carries the ball towards goal and crosses for Cristiano Ronaldo to score.

It was a dream routine from United, yet Howard Webb disallowed the goal and asked them to retake the corner. He had no idea what was going on, even thought it was completely legal.

MAN UTD'S CORNER VS CHELSEA IN 2009

And here's a shortened video of United's corner, but be warned, the quality is much worse.

Speaking afterwards, Sir Alex Ferguson revealed that he took inspiration from Celtic and had previously tried the corner at Aberdeen.

"Celtic used it in a European quarter-final in the year that they won it," he said. "[Bobby] Lennox and [Jimmy] Johnstone did it and I always hoped that I would be able to do it and pull it off at some stage of my career.

"I tried it when I was manager at Aberdeen but we never managed to score from it. And then we scored from it against Chelsea at last and it got chalked off!"