Southampton 4 Arsenal 0

Arsenal squandered their chance to go top of the table after crashing to their heaviest Premier League defeat for nearly two years.

The Gunners – who began 2015 with a shambolic performance at St Mary’s – produced a repeat on Boxing Day against a Southampton side who went into the game in atrocious form.

A stunning goal from full-back Cuco Martina put the Saints ahead on 19 minutes before Shane Long, with a brace, and Jose Fonte added further goals in the second half.

The visitors actually enjoyed the better of the early exchanges, with Olivier Giroud heading over from a corner and Nacho Monreal firing straight at Maarten Stekelenburg after a clumsy clearance from Martina.

Yet the Dutch defender – who only featured in the Saints starting line-up because of an injury to regular right-back Cedric Soares – shocked the visitors with a sensational long-range strike.

Ryan Bertrand’s cross was headed out by Per Mertesacker but Martina met the loose ball on the outside of his boot with a stunning half-volley that arced around the diving Petr Cech into the far corner.

James Ward-Prowse might have doubled his side’s lead soon afterwards, pouncing on a slip from Mertesacker before dragging the chance wide.

With the Saints growing in confidence, Long also found his way past the floundering Mertesacker and put the ball in the net, but was adjudged to have fouled the Arsenal skipper in the build-up.

Long had another opportunity to make it 2-0 before half-time, outpacing Mertesacker onto Sadio Mane’s through ball and lobbing Cech, only for his attempt to sail over the bar.

And the Gunners were fortunate not to concede a second soon after the restart when Virgil van Dijk headed in a Ward-Prowse free-kick, but a fractional offside call cut the celebrations short.

But the respite proved temporary as Long’s lay-off left Mertesacker and Laurent Koscielny all at sea and Sadio Mane sped clear before returning the ball for the Ireland international to stab past Cech.

Arsenal sent on former Saints youngster Alex Oxlade-Chamberlain for the final 25 minutes, but there were few opportunities for him to make an impact – and the game was soon out of their reach anyway.

Southampton skipper Jose Fonte rose above a static Gunners defence to head home his side’s third goal – and, with 20 minutes remaining, further damage seemed inevitable.

A flying save by Cech foiled Dusan Tadic, while Long hit the post and at the other end Mesut Ozil was unable to apply the finish to a cross from substitute Alex Iwobi.

Instead, it was Long who had the final word in injury time, running onto a pass from Oriol Romeu, holding off Monreal and firing past Cech to seal a miserable evening for the Gunners.

Arsenal: Cech; Bellerin, Mertesacker, Koscielny, Monreal; Ramsey, Flamini (Chambers 74); Campbell (Oxlade-Chamberlain 64), Ozil, Walcott (Iwobi 78); Giroud.