For this article I'm using Paul Riley's Expected Goals and Assists models, full explanations of which can be found on his site https://differentgame.wordpress.com. All the data I'm using in this article are available for everyone to see and sort on his Tableau page, found here https://public.tableau.com/profile/paul.riley#!/ (at the time of writing, accurate up to December 2nd, 2015).
The big problem is the attack
Riley provides an Expected Goals model based on the positioning of a team's Shots on Target throughout the season. This way we can see roughly how many goals Aston Villa could have been expected to score and concede based on the positions they are taking and allowing shots.
Villa's Shots on Target this season - orange dots are goals. Image credit to Paul Riley (@footballfactman on Twitter), data available at https://public.tableau.com/profile/paul.riley#!/
Villa's big problem hasn't been in defence (although under Remi Garde the numbers have been pretty bad). Riley's model has Villa allowing 22.23 Expected Goals, 15th in the league. Bad but not terrible.
That Villa have actually allowed 28 goals points to a mixture of bad luck and defensive blunders, allowing some dangerous set-pieces outside the box (Yann M'Vila and Gylfi Sigurdsson both scored excellent free-kicks against Villa) and Brad Guzan's worryingly frequent errors but even so the numbers are comparable to the other teams at the bottom of the league.
It's in the Expected Goals For that the real problems lie. Riley's model sees Villa with 11.95 Expected Goals scored, 20th in the league and well adrift of even Newcastle's 14.66 Expected Goals.
The problem isn't the strikers (apart from Abgonlahor)
As Villa have scored 11 goals, the team is actually matching up pretty well to their Expected Goals, which suggests that striking inefficiency has not been the problem.
This is borne out by Riley's individual player data. Jordan Ayew is showing impressive efficiency, having scored 3 goals compared to 1.79 Expected Goals, his strikes against Tottenham and Watford both scored from tricky positions.
Rudy Gestede is also fine, with 3 goals compared to 2.76 Expected Goals, putting away his chances as they come, though not scoring anything unexpected.
Only poor old Gabby Agbonlahor falls behind, with 0 goals from 1.49 Expected, having wasted reasonable chances against Leicester, Manchester United and Crystal Palace - none of which were appalling misses but you would expect a specialist striker to have converted at least one.
Villa's creative players aren't creating chances
Riley has taken these statistics a step further, with a model for chance creation, which measures not just where the shot was taken from but how the ball was delivered for the shot - open play or set piece, cross from out wide or a short pass inside the box.
This allows for a Expected Assists model, predicting how many assists a team's passes should have resulted in. Riley's model has Villa producing an expected 15.88 Assists so far, compared to 7 actual assists.
Villa's passes which led to shots this season - orange lines represent Assists which led to a goal. Image credit to Paul Riley (@footballfactman on Twitter), data available at https://public.tableau.com/profile/paul.riley#!/
Those total Expected Assist numbers are the worst in the league. The Expected to actual assists rate looks disastrous but it's worth noting that almost all teams drop quite far short of their expected assist numbers in Riley's models, possibly due to chances coming to non-strikers, e.g. Micah Richards' amazing failure to score against Sunderland.
Therefore the bigger worry is just how few chances Villa's creative players are contributing. Riley has a ranking of all players this year via their Expected Assists. Villa's top player? Ashley Westwood, in 71st with 1.66 Expected Assists, a number boosted via his set-pieces (he's at 1.03 from open play). He has one actual assist, his corner to Gestede for the winning goal against Bournemouth.
Second? Jordan Amavi, in 96th place with 0.86 Expected Assists which he outperformed handily by providing two assists before getting injured for the rest of the season.
Villa's supposedly top creative players, Jack Grealish and Carles Gil, sit in 158th and 206th place, with 0.39 and 0.26 expected assists from open play respectively. Neither have managed an actual assist so far. Although both have played significantly less minutes than Westwood, it's clear that Villa have struggled badly to connect the key creative players with the strikers.
Conclusions - problems across the field but above all in attack
Firstly, a quick disclaimer - the numbers can't tell the whole story and any data set is limited. For example Riley's Expected Goals Model is based on Shots on Target which may therefore ignore the inability of some strikers to actually trouble the keeper. It also lacks the most recent match which would probably make Villa's defensive record look noticeably worse.
However it can provide a lot of useful guidelines. Particularly here it's clear that Villa's problems wouldn't be solved by splashing money on a striker in January. Ayew and Gestede are converting the chances coming to them, the former at quite an impressive rate. They just haven't had that many chances.
Villa's defence is certainly in an issue, and watching the games it seems clear that there is a level of disorganization which is leading to conceding more goals than Riley's Expected Goals model would suggest, but it's not disastrously far behind the other relegation strugglers and might improve when the back-line is settled.
The real issue lies in the lack of connection between the creative players and the strikers. Grealish, Gil and increasingly Jordan Veretout are clearly players who have the ability to create chances but so far Villa haven't found a way to get them into key positions regularly. Part of that was Tim Sherwood's often baffling tactical decisions which saw Gil and Grealish placed out wide and Veretout essentially excluded, but Remi Garde needs to sort it out soon.