In Celtic terms, the recent signing of centre-back, Maik Nawrocki, was a significant transfer outlay, particularly for a 22-year-old.

This, along with some media chatter about potential transfer interest in Carl Starfelt, has triggered some debate and discussion within the Celtic metaverse about who is more likely to accompany Cameron Carter-Vickers as the primary pairing. While I have no particular insight into the likely decision-making process of Brendan Rodgers, this column is an attempt to flush out what may be some of the relative strengths and weaknesses between the two players.

First, let us begin with a review of Starfelt’s tenure over the past two seasons:

These two radars compared his past two league campaign minutes and were broken out by defending and ball progression-oriented metrics. They reflect what appeared to be a tactical tweak season over season, with Starfelt a bit less aggressive in ‘diving in’ to pressure opponents within their half but generally an effective on-ball defender. His volume of defensive actions was generally lower, more efficient and with the average distance closer to the middle of the pitch. The one glaring negative outlier for both seasons was the error metric, which StatsBomb defines as an on-ball mistake that leads to an opponent's shot.

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To place that metric into some context, Celtic as a team ranked in the 98th percentile among the global universe of clubs StatsBomb covers in shots conceded to opponents in the league last season, at just 6.82 per game. In addition, Joe Hart faced only 1.87 shots on target per game, amongst the lowest in all of world football, so needless to say Celtic do not concede a lot of shots domestically. Therefore, Starfelt ranking in the 16th and 22nd percentile in the error metric was contextually even worse, considering how few shots Celtic conceded overall. 

Those events are still relatively rare in the grand scheme of things, obviously, as Celtic defenders are simply not asked to defend all that much relative to most peers. Unfortunately for him and the club, Starfelt was not available for last season's Champions League, so we are left with a handful of group stage and final qualifying round games in the Europa League 2021/2022 season for a small sample size of how these potential issues manifested, or not, against higher quality opposition. 

We can see from the radar that compared with those handfuls of games with his 2022-2023 league minutes that his error rate exploded from 0.07 to 0.38, which was a wave that placed that performance metric in the first percentile. While this could certainly be a statistical anomaly from a relatively small sample size, it did align with this being a red flag within his domestic performance data. It also occurred absent a material change in the proportion of passes he made under pressure, which (not shown) was roughly 11 per cent in both data samples. 

How does Nawrocki compare? Firstly, the access to StatsBomb data was limited on Nawrocki to just Legia Warsaw’s 2021/2022 Europa League group games. However, a benchmarking exercise was completed for him using both Polish league and age-based peer benchmarks:

His sample size included a decent number of minutes, and his data profiles as an athletic centre-back capable of progressing the ball via carrying the ball at pace, a functional if unspectacular passer, with a mixed view via defensive-related metrics. It is also important to remember the context that Legia was a possession-oriented team within the Polish top-flight that finished second in both rates of possession and in the league table for the 2022/2023 season just completed. Like what he is likely to face at Celtic, he was not required to defend at a high utilisation rate given the team’s competitive standing, so the distribution of his volume-related duel metrics should be viewed within that context. 

His passing profile is quite different from that Starfelt displayed before arriving at Celtic in that Nawrocki was far more inclined to take risks with his passes. That was evident with his percentile ranking for metrics such as through-balls, passes to box and deep completions. A potential concern was that those high volume-related metrics took place within the context of his xA per shot assist and key pass per shot assist metrics benchmarking below average. 

This could raise a question as to whether his volume of creative and attacking output was more a product of his team’s system and competitive standing rather than his own idiosyncratic skills.  To try and gain additional insight into both players, the following two radars compared their relevant 2021-2022 Europa League samples: 

Firstly, some additional context. Legia’s group included Rodgers’ Leicester City, Napoli and Spartak Moscow, with Nawrocki having faced Spartak twice and the other two once each as a then-20-year-old. In fact, that is a vitally important context, as he remains a young player whose development curve likely remains steeply inclined at present. 

Nevertheless, that iteration of Nawrocki displayed some similar characteristics evident within the benchmarking profile conducted on his 2022/2023 league season in Poland. For example, we saw his turnover rate at a material level versus the comparatively safe passer in Starfelt. In addition, his metric for passing when under pressure displayed a low level of accuracy and a steep decline relative to his non-pressured rate. Perhaps notably, despite his relative youth and those other metrics, he did not commit an error that resulted in an opposition shot.

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Where does all of this leave us? Given Nawrocki’s age and potential for development under a coach such as Rodgers, the prospects of his improvement are exciting. Will that development arrive in time for the Champions League and derby fixtures fast approaching in a matter of weeks? Or will it be better to hope that Starfelt refrains from committing some of the errors that have plagued him so far at Celtic? 

Assuming Carter-Vickers will be fit and available, the inclination is for Nawrocki to be given the opportunity - given his potential upside on the ball, especially given Starfelt’s track record with errors. However, while we all likely hope he is ready to play regularly, that may be an unreasonable standard and he is bound to make some mistakes and/or be severely challenged at the Champions League level. Assuming he remains at the club, persisting with Starfelt would not be a surprise.