The De Gea Deficit

How many points would David de Gea's departure cost Man Utd? We do the calculations...

When Chelsea captain John Terry claimed last month that the signing of Petr Cech could be worth 12 to 15 points for Arsenal, supporters of the north London club were no doubt frantically doing their calculations. Now it's Manchester United fans busy with the maths. How many points would David de Gea's exit cost the club in 2015/16?

That's a difficult thing to quantify. Goalkeepers rarely score goals. They don't even get to boast of assists, while clean sheets fail to tell the full story either. And of course, much would depend on the identity of De Gea's replacement. But there are metrics that can offer some insight that goes beyond the anecdotal evidence of that save against Everton.

As with many defensive statistics, the key is not to judge the player's own work but the efforts of the opponent against him. It's here that the more in-depth Opta data can provide an interesting level of detail, as John Coulson, head of OptaPro, explained to Sky Sports. "We used to just collect shots, shots on target and where they were from," said Coulson.

"A few years ago, clubs asked us if they could have some sort of qualifier that distinguishes shots that were really clear-cut chances from regular shots. That's something that we've added. From that, we can derive a goalkeeper's save percentage versus his save percentage when he's in a big-chance situation."

The data is particularly revealing when it comes to De Gea. United's porous defence might have been overstated somewhat given that manager Louis van Gaal's side actually had the fourth-best defensive record in the Premier League last season, but the criticism was not without substance as the underlying data shows.

According to Opta, no Premier League side made more unpunished errors than United. It was the last line of defence that so often proved vital and the statistics for clear chances – defined as "a situation where a player should reasonably be expected to score usually in a one-on-one scenario or from very close range" – emphasise this point.

There were 1,200 clear goalscoring opportunities in the Premier League last season. Of these chances, on average, 58 per cent of them did not result in a goal. If that means we need to rethink the definition of 'a sitter', it also highlights De Gea's ability in such situations. When opponents were faced with the Spaniard to beat, as many as 68 per cent were missed.

If that difference doesn't sound too dramatic, consider its impact. United allowed 53 such opportunities for their opponents in the 2014/15 season and teams scored against them on 17 of those occasions. With the average Premier League goalkeeper there to stop them, statistically it ought to have seen 22 goals going into the United net.

A five-goal difference. Not a lot? Well, it depends which five goals that De Gea's brilliance kept out. Examine the detail and there is a strong body of evidence to suggest that his saves were particularly significant. The importance of his work becomes clear when looking at the 10 games last season when the team missed more than one clear chance against United.

There were four away games in which Van Gaal's team surrendered two or more clear goalscoring opportunities against them. Not only did United manage to win three of those matches – at Arsenal, Southampton and Newcastle – but they won each of them by just a solitary goal. The big misses. The big saves. They were the difference.

The other six games were at Old Trafford. One, against Southampton again, was lost anyway. Another was the 3-0 victory over Liverpool that ostensibly might have been won regardless, although it's worth noting that De Gea earned the man-of-the-match award with several of his crucial saves coming with the game still in the balance.

But the other four matches were all tight. There were the 2-1 victories over Everton and Stoke and the 1-1 draws with Chelsea and Arsenal. In the latter game against the Gunners, the equaliser even came following De Gea's substitution as Victor Valdes appeared to be wrong-footed a little too easily from Theo Walcott's deflected centre.

Five goals then. A one-goal swing in five of those matches - the ones where it's most likely that De Gea's presence made the difference – could change the picture of United's season considerably. While the best-case scenario would see the side surrender only two points, the worst-case scenario would equate to five games drawn rather than won. Ten points lost.

That outcome would have been enough to leave United languishing down in seventh spot for a second consecutive season. Below Tottenham. Below Liverpool. Below Southampton. Closer in points terms to relegated Hull than champions Chelsea. And without Champions League football once again.

Following United's summer spending spree, there is an understandable air of optimism. Van Gaal knows he must tighten up the defence and his team will surely benefit from another pre-season with their manager. But for all the positives, the loss of David de Gea could undermine that progress. In fact, United might need to find 10 points from somewhere just to stand still.

Credit: Skysports.com