The key Celtic passing factor Rodgers must address - Alan Morrison

That is not surprising as StatsBomb is a commercial organisation seeking to maximise profit above everything else. OBV is part of their intellectual property. There has been a reluctance to share those metrics in articles as it does not feel worthwhile to quote data that I do not fully understand. How can conclusions and summaries be drawn if that were the case?

So, it was great to see this tweet published along with the attached video. It seems every action is assigned an expected goals value as regards whether it hindered or aided your team's attempt to either score or prevent a goal. There is still scepticism about the utility of that, and we can have a further theoretical discussion about the efficacy of reducing complex actions down to single metrics. But let’s accept it for what it is. And let us get onto another vital analytical topic – benchmarking. All data points may be potentially flawed due to the mixed definitions of the data elements, the different perspectives of the capturer (was that an interception, a challenge or a duel?), and the variable data management practises around the storage and retrieval of that data.

It’s a minefield. But what is valuable is the ability to compare apples with apples. That is why it is worthwhile to collect one's own data, despite the plethora of commercial data providers. If it is consistently defined, interpreted, captured and stored, it then allows for Celtic players to be compared against each other – the perfect benchmark as many of the conditions are similar.

Back to StatsBomb and OBV. It is worth sharing two of their OBVs that relate to ball progression. Why? Because passing covers the majority of the on-ball actions any player attempts (around 75 per cent of all on-ball actions are attempted passes). And because ball progression in general will be key for Celtic under Rodgers as a possession-dominant side tasked with breaking down stubborn defences. Pass OBV covers this. Related to that, it is also worth including OBV (D&C OBV) – i.e. getting the ball forward by running with it at your feet. StatsBomb has calculated their values going back to 2018-19, so the last season under Brendan Rodgers. This analysis has been split into four broad positional categories.

Full-backs

Here are all the full-backs with sufficient SPFL minutes plotted as regards pass and D&C OBVs:

The elite ball-carrying ability of Jeremie Frimpong stands out the most. Celtic do not currently have anyone that comes close to that level of ball progression with the ball at their feet. That is an elite-level skillset that appears to attract big money on the market. It is surprising that a declining Emilio Izaguirre - 2018-19 vintage - has the highest pass OBV of recent times. Behind are Mikael Lustig and Kieran Tierney - also of that era.

Greg Taylor and Anthony Ralston have got close to the 2018-19 cadre level but not last season. Alistair Johnston does not profile well by this data but if you looked at the packing data, then he would be a standout. For Rodgers, he may notice that his full-backs do not have the ball progression stats he had to work with the first time around - far less anyone who really stands out.

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Centre-backs

This was something of a problem position in Rodgers’s first tenure, with him failing to have a consistent year-on-year partnership. Progression data for this group:

The top right sees the pocket of Kristoffer Ajer’s collection of seasons in scope. His outlying ability, like Frimpong, was ball carrying. However, again surprisingly, Moritz Jenz last year and Jozo Simunovic in 2018-19 both had higher per 90-minute D&C OBVs. It would be surprising if they had a higher volume of carries, but maybe they chose their moments wisely, thus boosting their averages.

The current centre-backs had the higher pass OBV, but for this position of centre-back, consider the impact of team instruction and stylistics. Most managers will prefer how they wish their backs (and indeed goalkeepers) to work with the ball at their feet. Some may simply launch it (most of the SPFL); some will ask to keep it simple as Rodgers did with Dedryck Boyata; whilst Ange Postecoglou wanted more aggressive ball progression from all players.

Stephen Welsh, in 2021-22, was the outstanding passer, according to StatsBomb from this peer group. It is a strength of his game but whether he gets to develop further these skill sets at Celtic remains to be seen.

Both Cameron Carter-Vickers and Carl Starfelt have been able to improve their pass OBV relative to recent peers under Postecoglou, so may be able to improve again under Rodgers.

Midfield

This covers more traditional midfielders as opposed to wingers or number 10s:

Some more interesting outliers here. OBV likes Aaron Mooy, and who wouldn’t? He will be a big loss to Celtic, and not just his raw passing, but the context and timing of his efforts. He sensed well when to go long, short, aggressive or passive. His profile is most like that of an NFL quarterback.

Of current midfielders, Matt O’Riley’s initial season produced the nearest anyone has got to Ryan Christie’s 2019-20 season. O’Riley fell back last season, but some of this may be down to the prolonged stint covering Callum McGregor’s position.

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Reo Hatate shows the most potential for ball carrying with the high-water mark being Olivier Ntcham’s 2018-19 campaign (under Rodgers). This may be encouraging for Hatate, who might find Rodgers inspires him to similar heights. As - and the packing data backs this up - Hatate’s passing OBV disappoints. Yes, there is the occasional worldly through-ball in there, but a lot of average stuff as well.

You can see how both Scott Brown’s and McGregor’s seasons have oscillated around a low variability of outcome. With consistency comes some predictability of data outcome.

Attacking Midfielders

This covers the wide attackers and number 10s. Both David Turnbull and Christie appear in both charts based on where, predominantly, they spent seasons positionally.

This is a fascinating view. Why? Well, the degree to which Celtic will miss Jota, as well as Mooy, should be clear. Jota is a fantastic combination of pass, dribble and carry OBVs. On the face of it, Sead Haksabanovic looks a good replacement. Yet the eye test tells us he lacks the pace to be effective in that wide role, especially against better opposition.

Similarly, Turnbull. Very high pass OBV, and a modest carrying OBV, yet - like Haksabanovic - possibly just not enough power and pace to be a Rodgers player. The manager has spoken about how loves Liel Abada, and he is joined in that regard by most data. Expect big things from the young Israeli this season.

The decline of James Forrest is mapped a little ruefully by this view, and StatsBomb models really did not like Tom Rogic either. Those calling for the return of free agent Mohamed Elyounoussi will not be joined by the StatsBomb team, also. Daizen Maeda does not show up well as a winger by these metrics and it may be fortuitous for him Rodgers has discovered what an exceptional striker he can be.

If you are wondering why Celtic are buying so many wingers, this view may help understand that.

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Summary

StatsBomb OBVs have been better explained and I like the concept in terms of seeing every move being assessed in terms of the ultimate objectives of scoring and preventing goals. A little over simplistic, but aren’t all models? It could be argued it needs complementing with packing data and chance creation data for a fuller, more contextual picture. Alistair Johnston is underappreciated by these measures, probably the most glaring example. 

However, Rodgers may want more from his defenders in this regard than is shown here. He will hope he can develop Hatate and O’Riley, and Abada amongst the wingers has the most obvious potential as regards ball progression. Plenty to work with, but also some glaring gaps in the squad. More patience and a busy window beckon.