Where Portsmouth's John Marquis ranks in the XG stats and why he can only watch on with envy as Peterborough and Sunderland duo lead the way

The Pompey striker failed to convert any of his three shots on target during the goalless draw at The Alexandra Stadium, including a penalty which was comfortably saved by keeper Will Jääskeläinen.

It contributed to the Blues returning home with only a point and slipping to sixth in the table.

Marquis, who went into the midweek game having had injections on a troubled ankle during a three-match ban, has recorded 14 goals and four assists in this league campaign – making him Pompey’s top scorer in the division.

But data from the football scouting platform Wyscout shows he could have scored a lot more, given the quality of the scoring chances he’s had.

Expected goals (xG) is a metric which determines the likelihood of a shot being scored.

A shot’s probability of being converted is calculated by its location on the pitch, the position of opposition defenders and if it’s a headed chance, among other factors.

The higher a shot’s xG, the more likely it is to be a goal.

If a player has a shot that’s worth 0.6 xG, you would expect them to score 60% of the time.

Marquis has an xG of 17.22, 3.22 higher than his 14-goal league tally – the second largest difference in the league for attackers who are scoring below the chances they have been presented with.

Only Bristol Rovers striker and former Blues target Brandon Hanlan has a larger negative difference between his goals and xG tally, only finding the net seven times from his 14.24 xG.

Meanwhile, the stats don’t look favourably on Lincoln’s Jorge Grant (11 goals from 13.43 xG) and MK Dons’ Scott Fraser (13.35 xG), whose goal tally should also be a lot higher than their 11-goal returns respectively.

Marquis’ expected goal statistics also pale in comparison to the league’s most prolific attackers.

Peterborough’s Jonson Clarke-Harris – top goal scorer in League One – has lived up to his expectations by finding the net 28 times from his 27.17 xG total.

The second-highest scorer, Sunderland’s Charlie Wyke, has vastly exceeded his 17.6 xG by scoring 24 times, consistently converting difficult chances.

The larger the negative difference between a player’s goal total, and his xG, the more chances they are failing to convert.

In the match against Crewe, Marquis failed to score from his 1.13 xG, which is hardly surprising given his missed penalty and his chance with an unmarked header in the 57th minute.

Cowley will no doubt be aware of such statistics.

But the message to his Pompey players is clear – remain positive.

He told The News after the draw at Crewe: ‘I think there’s some work to do in terms of the positivity.

‘Sometimes we are quick to be critical.

‘It’s hard. We want to do so well, but only a couple of them, get frustrated quite quickly.

‘I just want them to stay positive.

‘I don’t like negative body language, I don’t like anyone who is going to sap my energy.

‘I’ve got loads of energy and enthusiasm and I want us all to know how fortunate we are every single day.’