Celtic's full-backs: Why and how they've changed under Brendan Rodgers

Clearly the rear of the team has been subject to most injury impact, and Alistair Johnston has only recently returned from a long-term break.

There was also much transfer window speculation around whether a new left back competitor for Greg Taylor would be sourced. He was not.

As we look forward to the end of the international break, Johnston and Taylor are firm first picks. And with two Champions League matches completed, and Celtic’s defensive alignments being tweaked by Brendan Rodgers, where are the full backs compared to last season?

SPFL – Greg Taylor

Statsbomb compares Taylor’s SPFL performance over the past two seasons:

Greg Taylor's stats for the season against last (Image: StatsBomb)In general, this season he is profiling more like a traditional full back with less deep progressions, and less defensive activity in terms of both tackles and aerial duels.

His rate of turnovers is up and in tandem his passing accuracy is down which may be a form thing.

What has risen is the number of pressures he is applying, not as important in the inverted role which was more about defending space out of possession.

Whilst form has improved in the last two matches, it seemed Taylor was off the boil early in the campaign and these numbers reflect this more than any change in role. Perhaps he was unsettled with the left back chatter in the transfer window?

SPFL – Alistair Johnston

Similar view for Johnston:

Alistair Johnston this season vs last (Image: StatsBomb)

The number of pressures from Johnston has increased to an even greater extent (from 9.34 to 14.17). We may be onto something here about the tweaks from Rodgers related to his wide defenders.

Like Taylor, Johnston’s deep progression and passing percentages are also down.

And he is doing more defending as regards volume of tackles and aerial duels.

Celtic have been more under pressure this season than last where Postecoglou’s sides simply overwhelmed the opposition on Scotland to a ridiculous degree.

But across both players there is evidence of less emphasis on ball progression (that inverted central passing), more defending and more pressuring the opposition.

Defending – All Competitions

Using my own data, I aggregate all defensive actions into two composite metrics.

Defensive action success rate measures the percentage of defensive actions that the player “wins” irrespective of what happens to the ball and therefore possession subsequently.

Possession won from defensive actions measures the percentage of defensive actions that result in Celtic having the ball after.

Here is the comparison for both players across all competitions/matches:

Defensive comparisons (Image: AM)

Whilst Statsbomb records a count of events, this data considers the outcome.

Johnston’s success in winning possession back from defensive actions is down from 77% to 68% and his defensive actions success rate has improved from 65% to 62%.

Meanwhile Taylor’s defensive metrics have gone up as I reported in an earlier article.

More (slightly mixed) evidence of more traditional defending from the full backs and given Celtic’s tough opening schedule of away matches and Champions League ties, maybe no surprise.

Let’s turn to ball progression.

Pack Passing

Under Postecoglou, the inverted full backs were encouraged to pass quite aggressively through opposition lines from a more central position.

Indeed, Johnston had the highest average pack passing score per 90m of the whole squad with a score of 82.

Has this changed under Rodgers?

Pack scores for the full-backs (Image: AM)

Both players average pack passing scores have reduced since last season and Johnston’s remarkably so – from 82 to 51. Taylors from 65 to 62.

Again, we cannot rule out the impact of a tough schedule of matches, including playing with nine and ten players in two matches.

And certainly, Taylor’s reduction is less significant.

With Johnston though that is a huge drop off.

My eyes tell me he is playing more as an overlapping full back in the more traditional sense and is less seen in the middle of the park. Whereas Taylor seems more comfortable coming inside and continuing a similar role as under Postecoglou.

Here are their respective heat maps for the season so far (league games only, courtesy of Sofascore):

Heat maps for the full-backs (Image: AM)

Here we can see that Taylor is much more likely to operate off the flank whilst Johnston tends to maraud closer to the touchline and is less likely to receive the ball infield in his own half.

Is this working to orders or Rodgers letting the players play to their strengths?

Chance Creation

Finally let’s consider the state of play as regards final third chance creation.

This covers all competitions and reflects the volume and quality of chances created from open play.

Chance creation totals (Image: AM)

It may surprise you that Johnston has the higher xA of the two both this season and last. Indeed, this season his xA90 has improved from 0.19 to 0.25. An aspect of Saturday’s victory over Kilmarnock that was particularly enjoyable was the interplay between Johnston and Matt O’Riley down the right side.

Reverting to a more tradition full back role seems to have enabled Johnstone to elevate his attacking productivity.

Whereas Taylor’s has reduced some both in volume and value of expected assists / chances.

Summary

It is still early, and sample sizes are small, and we must consider the context of the matches player and the standard of the opposition.

However, early trends of full back play suggest that Rodgers is flexible in allowing his two first picks to play the game they are most comfortable with.

Namely, Taylor, who as a youngster was a central midfielder, is happy to invert and see the game from a more central position.

Whilst Johnston, more of a direct athlete, seems happier playing up and down the line in the manner of a more traditional wing back.

Both players are being asked to press more which I suspect is team orders.

The discrepancies in defensive performances I suspect are an early season feature of form rather than any tactical tweaking – there aren’t clear enough trends.

I think both players are starting to find better form having recovered from injury in Johnston’s case, and perhaps feeling under threat in Taylors.

But whereas Postecoglou was precise and prescriptive of the role he asked of all his players, it seems Rodgers is more minded to let players be comfortable to their strengths, albeit inside his framework.