Chelsea have opted for an unconventional method to prepare for their mouthwatering Premier League clash against Arsenal at the Emirates Stadium on Sunday.

Chelsea boss Xabi Alonso deployed his players against members of staff armed with rugby tackle pads, preparing the Blues for the physical onslaught they are expected to face from Arsenal’s big and powerful defenders, particularly in set-piece situations.

Midfielder Valentin Barco, left-back Pep Chavarria, and defender Josh Acheampong were spotted holding crash pads while their team-mates crashed into them at Cobham -- an unusual but rather fitting way to prepare for what could be coming from the Arsenal playbook.

The term refers to the detailed tactical strategies and painstakingly rehearsed set-piece routines developed by manager Mikel Arteta and set-piece coach Nicolas Jover -- routines Arsenal have used to devastating effect over the past few seasons.

Arsenal ended a 22-year wait for the Premier League title in May and came within a penalty shootout of winning their first Champions League last season. Set-pieces played a major part in that success.

The Gunners scored 25 goals from set-pieces in the Premier League this season, excluding penalties -- the highest total in the division -- while also setting a new record for goals scored from corners in a single campaign, with 19.

And there is far more to it than simply throwing the ball into the box and hoping one of the giants gets on the end of it.

Arsenal crowd the penalty area and often station several players inside the six-yard box, creating chaos and disruption by blocking opponents and restricting the goalkeeper’s access to the ball. Dummy runners add another layer of misdirection, dragging defenders away from the areas Arsenal actually want to attack.

There is also the art of hiding in plain sight. Players can begin near the back post, where defenders are forced to keep track of both their markers and the ball, before suddenly making their way towards the centre of goal. By the time the ball arrives, defenders can find themselves chasing shadows.

Then comes isolation -- putting Arsenal’s most dangerous aerial threats into one-versus-one situations away from the main action, or simply creating enough space for them to attack the ball freely.

Screens are used. Attackers block runs. Timed dashes towards the near post help players escape their markers and win headers.

None of this is exactly a secret anymore. And yet, that is perhaps what makes Arsenal’s set-piece dominance all the more remarkable.