Another week, another fantastic Lionel Messi goal.

Barcelona headed into Sunday's trip to Villarreal knowing they needed to win to re-establish their five-point lead at the top of La Liga - and that's exactly what they did.

It wasn't easy, though. Villarreal held Barca until the 72nd minute, when Luis Suarez made it 1-0, having gone down to 10 men 12 minutes earlier.

Messi then struck in the 83rd minute to double his side's lead and guarantee an important three points.

Sergio Busquets intercepted and passed to Messi, who humiliated two defenders to go one-on-one and made no mistake in firing past the goalkeeper.

It means the Argentina international now has a staggering 525 goals for Barcelona, equalling Gerd Muller's haul for one club (Bayern Munich) in Europe's top five leagues.

Messi can break the long-standing record on Sunday, when Barca host Deportivo La Coruna at the Camp Nou.

However, there's a bizarre reason why Messi's goal at the Estadio de la Ceramica technically should have been disallowed by the referee.

In the highlights reel below, as Messi bursts through Villarreal's defence, you can see there is a second football on the pitch near the corner flag in the top left.

And as many football fans rightly pointed out on Twitter, the referee should have stopped play before Messi's goal or ruled it out completely. Check it out at 10:02.

MESSI'S SOLO GOAL VS VILLARREAL

Did you see it? Here's a screenshot.

It would have been very harsh from the referee to disallow Messi's goal, especially when it was Villarreal who restarted play with two balls on the pitch, but rules are rules.

Luckily for Messi and Barcelona the referee didn't notice and the goal stood, which meant they won 2-0, went five points clear of Valencia and increased their goal difference to +31.

Ernesto Valdere's side are unbeaten in 15 La Liga games and should they avoid defeat against Real Madrid on December 23, it'll be a wonder who exactly can stop them.