Arguably James McCarthy had the most effective game of his fledgling Celtic career, away St Johnstone.
Filling in amongst a COVID and injury ravaged squad, he fulfilled the sitting midfield role (or “6”) in a midfield three.
Saintly McCarthy
Some of his numbers were eye catching in that ultimately comfortable win.
He led the team with 13 successful challenges / Interceptions – 3 more than the next highest, whilst being unsuccessful with only 1.
He won back possession 7 times, also a team high.
His 12 Pack passes were the most of the midfield three.
What was also telling was that there were 0 assisting passes and only 1 secondary assisting pass. And 0 efforts at goal in a side attempting 25 shots.
Peer Comparison
McCarthy hasn’t quite played the requisite 900 minutes for Celtic (594) but I reckon I’ve seen enough to get a sense of what the player is capable of.
And, possibly more importantly, what he is not.
Such has been the longevity of Brown, that peer comparison with other natural “6” holding midfielders is difficult. We have McGregor, Bitton and Soro this season such have been the constant injury enforced changes, and Soro in 20/21.
Defensive Metrics
Firstly, the key defensive metrics of Defensive Action Success Rate (DASR) and Possession Won from Defensive Actions %.

I mention again how it is generally small margins between all players on most metrics. I reinforce this to emphasise how far ahead (with a small sample) McCarthy’s defensive data is from the peer group.
He is successful with 75% of his challenges and interceptions, and wins back possession with 85% of his defensive actions. That number profile would be decent for a centre back.
Bitton’s numbers from this season show how effective he can be in this role.
Soro’s form has slipped since his lively introduction to the team in late 2020.

The above shows Recoveries – a proxy for anticipation, positioning to pick up lose balls, and Defensive 3rd Wins (i.e. winning the ball back in your own defensive 3rd of the pitch) - both per 90m.
These were where Brown was particularly strong even in his declining years.
Soro was particularly actively aggressive winning the ball back in his breakout season but has regressed badly this season.
McCarthy is as close as anyone to Brown’s output by these metrics.
McGregor is a completely different type of player to the others, as shown.
The debate whether Celtic need a McGregor type player at 6 or a McCarthy type player, is a great one to have.
Ball Progression
Here we plot Pack Passes (forward passes that take out opponents) and Ball Carries (Progressive Runs plus Pack Dribbles).

Here, unsurprisingly, McGregor comes to the fore, with marginally the greater Packing rate, but a slightly lower Ball Carry rate than a revitalised Bitton.
This is where Brown struggled in the later years and with Postecoglou looking for more aggressive lateral passing but with possession maintained, the former pair are a better fit for this style.
McCarthy is ok at ball progression but doesn’t get on the ball as much as McGregor or Bitton. He is also the least productive progressing the ball at feet. If anything, he looks less mobile than 35-year-old Brown.
Soro had a good mix of both but is likely not a good enough passer for this standard.
Creativity
Here we plot Secondary Assisting Passes (the pass before the assisting pass that results in a shot) and xA (Expected Assists) per 90m.

Bitton, Brown and Soro are in a tight group of players producing less that 0.1 xA per 90m and less than 1.3 secondary assisting passes per 90m.
McGregor is clearly the most creative in this role with xA over 0.17 per 90m and over 1.4 secondary assisting passes.
McCarthy has the lowest secondary assisting pass rate, but the highest xA per 90m. This anomaly may be a “small sample” issue as he has only supplied 6 chances but 4 of them had relatively high xA values. I suspect this will revert down in time.
Conclusion
This wasn’t intended as a thorough review of all Celtic’s defensive midfielder options but I hope you have a sense of the playing field in this position.
As regards McCarthy, he has a highly specific skill set in terms of successful defensive actions that are show rates more akin to an out and out defender. His ball progression is average at best in passing, and almost non existent carrying the ball. Creatively, he will offer very little when the numbers settle down.
We can see with our eyes a highly immobile player relative to the high energy system Postecoglou is trying to implement. Bitton moves like a young gazelle in comparison.
This particular specialism will have utility in closing games out and in particular circumstances away from home against tougher opponents. But this is not a player who will be a pivot around which “Angeball” is constructed.
I suspect Ideguchi will provide more clues as to what Postecoglou wants out of his “6”, but in the meantime I expect McGregor and Bitton to be preferred (when / if fit!).