Heading for Trouble?

Celtic conceded two goals from set plays against Aberdeen. This triggered the usual dual response from pundits and some supporters alike bemoaning Celtic’s ability to defend crosses and set plays in particular.

But, is this fair?

Context

Firstly, kudos to Aberdeen for two well executed set plays from Ojo.

Both were very well delivered.

The free kick routine for Ramirez’s goal is one Celtic should be familiar with as both Sinclair and Rogic have scored from it in recent times. Perhaps the influence of Scott Brown, who was expert in blocking off Starfelt’s defensive action.

The second free kick was another perfectly flighted cross to Ferguson’s head. He was matched up with Taylor who must be a good 7 inches shorter. From 6 yards out and a firm contact, Hart had no chance.

The combined xG from these two chances was 0.35. So, 2 goals are Hatate levels of effectiveness.

Aberdeen average 0.32 xG from set pieces per match. This places them in the 76^th % for the SPFL. Indeed, their average xG per shot of 0.09 is one of the lowest. These two facts are not unconnected.

Relying on set plays for chances means lots of low xG shots/headers. But, Aberdeen are one of the best at it. Here is a link to a thread by @coachchrismcl on twitter highlighting Aberdeen’s creativity from set plays.

Postecoglou said post-match “Set pieces were obviously a threat. They are a big, physical team and, with good delivery, and we didn’t handle the set piece situation well, which is something we need to improve on”.

So, bad day at the office, or systemic weakness?

Comparison

Here is Celtic’s xG against from all set plays (corners and free kicks) from both 1^st (direct pass) and 2^nd (the attacking action immediately following the 1^st pass) phases of play from 2017-18 to the current season:

Prior to the Aberdeen game this season’s average was a lowly 0.11 xGA per 90m. Goes to show what 1 game can do. That one game has pushed the average up to 0.19. This is better than last season but higher than the previous three.

Last season was a nightmare from start to finish with an endless stream of “what could go wrong”.

Performances in defending set plays was no exception. (Sidebar: I do like the idea of getting all your crap and bad luck out the way in one season though).

Overall, I’d say that we are improving (how couldn’t you?), but as the gaffer says, work still to do.

Perception

The perception of Celtic’s set piece effectiveness is driven in part by outcome rather than actual defensive (and other teams’ attacking) performances.

Which is a roundabout way of saying folk are influenced by the actual goals conceded.

What we can see is that actual xGA from set plays is pretty stable across five seasons at around 10 goals.

What is more variable is actual goals lost.

Conceding less than expected in 17/18 and 18/19 may well be construed as “good” performance, and conceding way more than expected last season and this as “bad”.

Even the recent defensive bedrock high point of Ajer and Jullien in a dominant 19/20 season conceded slightly more than expected.

Of course, it may not be “good” or “bad” merely the vagaries of fortune in a low scoring sport.

xGA went up slightly last season and we can understand that given the changes to personnel, injury to aerially dominant Jullien, and the general lack of defensive cohesion.

Should We Be Worried?

You probably get the sense I am not as excited about this as others are. I certainly believe that any club should seek to make small marginal gains across all aspects of performance and certainly set piece play at both ends. I also know that set piece chances tend to be low xG and that perception often overshadows reality.

I am worried to the extent that there are clear structural issues Celtic need to address.

Simply, we are not a big team! Carter-Vickers and Starfelt are barely 6 feet, and the rest of the side much smaller. This means match ups like Ferguson v Taylor will continue to pose a risk.

What I have also observed is a general improvement, as across the board, in levels of set up and organisation. Another non debate in my eyes is the zonal vs man to man debate for defending corners and set pieces. Postecoglou, who seems a very sensible and pragmatic man, adopts a hybrid approach. That is, the taller opposition players are man marked, whilst the remaining players patrol the zones you don’t want to leave free across the 6-yard box.

My opinion is that this is the most sensible approach to take based on conversations with coaches, as opposed to an “all in” zonal or man orientated approach.

You always risk conceding goals due to good delivery, movement, a personal mistake. And, as mentioned, Celtic carry additional risk from being a relatively small team.

Summary

Celtic’s defensive performance from set pieces can continue to improve as although Postecoglou has tightened it up and implemented a pragmatic hybrid system, they lack an aerially dominant centre back, and the team is still earning the patterns.

Conceding two to a team that specialises in such situations was disappointing but not career ending.

As always, I’ll continue to monitor.