Michael Jolley utilised man-marking in an attempt to get his Grimsby Town side to shut down Chelsea. It obviously didn’t work.

Given it took Chelsea just minutes to open the scoring, perhaps we can learn why it didn’t work by looking at Ross Barkley’s goal. Who’s man is who is indicated by lines where possible.

The move starts in Chelsea’s half where Marc Guehi has the ball and exchanges passes with Billy Gilmour. Grimsby striker James Hanson is tasked with marking both Guehi and his central defensive partner Kurt Zouma. Having just closed down Zouma, Hanson doesn’t really manage to get across and put any real pressure on Guehi and the youngster opts to push forward on the ball, with Hanson quickly giving up on following him.

Guehi exchanges passes with Gilmour

Guehi receives the ball back from Gilmour

Guehi pushes forward on the ball

Two immediate flaws with man-marking are exposed when Guehi continues forward on and on – and then some more – without being closed down by Grimsby. Firstly, Hanson has left Guehi and, as no one else wants to leave their man, there’s no one to pick up Guehi until he reaches Grimsby’s one spare man, Harry Davis. (To his credit, Harry Clifton does leave Barkley free to cover, however he reads the unfolding situation well, realising Davis is in position to stop Guehi advancing and that the bigger threat is Michy Batshuayi making a run in behind, having lost his marker Mattie Pollock.)

Secondly, Grimsby’s positioning is entirely reactive to Chelsea’s. Grimsby players base their positions on where the Chelsea players are and as a result Chelsea can manipulate Grimsby’s players to leave large gaps open to exploit. This leaves space between Grimsby’s players for Guehi to run straight through, getting from back to front in seconds.

This manipulation is also shown by Batshuayi’s movement. The Belgian drops deep, pulling Pollock with him then turns around and sprints in the opposite direction. As he’s faster than Pollock, he can run past him and into the space that Pollock’s left to follow him.

Guehi pushes forward into Grimsby’s half and Hanson leaves him. No one closes him down, preferring to stay with their own men. Batshuayi drops deep, pulling Pollock up the pitch.

Guehi continues forward with the ball. Batshuayi makes a run forward, getting ahead of Pollock.

Guehi opts to stop dribbling forward when he meets Davis. As he gets nearer, he slows down and Davis steps out to meet him, then Guehi slips a pass in behind him. Both Batshuayi and Christian Pulisic have made runs into the space and are met by Pollock and Clifton, both following Batshuayi. Liam Gibson is supposed to be marking Pulisic but he seems to be reluctant to follow him, leaving it late before moving across. The American moves very quickly but Gibson seems late to follow even taking that into consideration, presumably expecting Jake Hessenthaler to pick him up, passing Pedro Rodriguez on to him. It’s only when Hessenthaler doesn’t move despite Pulisic making a run straight in front of him that Gibson begins to move across, realising Pulisic is his sole responsibility.

Guehi slips a pass in behind. Pulisic and Batshuayi make a run into the gap.

Pulisic collects the ball and makes probably the worse choice available: shooting at goal from a mediocre angle blocked by three defenders. Unsurprisingly, the ball is blocked and cleared away to Gilmour near the edge of the area.

Pulisic collects the pass

Pulisic shoots into a crowd of players

The ball is cleared to Gilmour

Gilmour quickly controls the ball and drills it into the feet of Pedro, who lays it off for Barkley. Clifton has just gone sprinting into the box to cover his teammates yet he’s out to Barkley quickly. The scouser soon notices the acres of space to his right though, with three Grimsby defenders all within a metre or so of one another, and he eases past Clifton, dribbling into the box and firing a shot past James McKeown.

Gilmour passes to Pedro

Pedro lays the ball off to Barkley. Clifton is quickly out to meet him.

Barkley dribbles past Clifton. Grimsby’s defenders are all clumped together in the centre, leaving a massive gap on their left.

Barkley beats Clifton and attacks the gap

Barkley shoots and scores

Barkley showed another problem with man-marking: it requires you to win your one-on-ones. If you are a League Two team going against a Premier League side, your players might not have the quality to come out as the better team in individual battles and won’t have anyone to cover for them. Only Pollock comes across to close down Barkley once it’s clear he’s beaten Clifton, with everyone else preoccupied with their own men.