MARTIN KEOWN: Man United's abysmal corners could cost them top-four

Manchester United's set-piece struggles are nothing new. 

Previous manager Ole Gunnar Solskjaer identified this as a problem, so much so that he hired a specialist set-piece coach called Eric Ramsay to try to improve them. 

When you consider the players United have at their disposal, this is an area in which they're massively under-achieving. They've got more than capable deliverers of the ball in Luke Shaw and Bruno Fernandes, and they have prime targets in the box in Harry Maguire and Cristiano Ronaldo, among others.   

Despite this, United remain the only Premier League side yet to score from a corner this season. Maguire, United's best header of the ball, is used far more purposefully for his country than he is by his club. 

For England, he is the main man from set pieces, either moving to the far post to head back across the goal for others to score or towards the middle so that he can score himself. Ralf Rangnick cannot underestimate the importance of set pieces and the part they can play in the success of United's season. 

Though the biggest clubs focus on possession football, they're also at the top of the table for creating chances from these restarts. Liverpool have scored a league-high 15 corners since United last scored from one. 

It isn't only a tactic for teams lower down the table to try to nick a goal and get a win. It's something that elite coaches and clubs work on extensively. 

A huge effort is made to analyse their upcoming opponents with a team of specialists looking at their opposition's strengths and weaknesses from restarts in great detail, from the signal they give at the start of each routine down to the precise movement of every player. 

They're always looking for the slightest edge, and the