Celtic were once again bitten by a set-piece goal as Filip Helander headed Rangers to Glasgow derby victory on Sunday.

The defending at the goal, which came from a corner, has been the subject of much debate over the past couple of days and prompted some of the Scottish football commentariat to sift through their cupboards in search of the blame game. 

Here, The Celtic Way dissects what actually happened for Helander's Ibrox winner.

Starfelt and the "Celtic just can't defend set-pieces" narrative

Some of the discourse surrounding the goal has focused on the role of Carl Starfelt, with ex-Celtic striker John Hartson saying on Sky Sports after the game that the Swede "had to head that ball" and that he "has to be big, strong and brave - and he simply doesn't do that".

Others raised the suggestion that the side's inability to defend set-pieces has now simply become ingrained, with another former Celt, Packie Bonner, telling BBC Sportsound that "they lost the game because from set-pieces they don't have the players that can actually defend them at the moment".

On Sportscene, meanwhile, former Hibernian midfielder Michael Stewart pointed out potentially those eyes being drawn to Starfelt were not seeing what they initially thought and that clever movement from Helander coupled with Stephen Welsh's positioning was the key.

But which is the case? Do all of these views have merit? Let's take it step-by-step.

Helander's free run

Celtic Way:

The television camera angle is not great overall but this freeze-frame is interesting as it almost gives us a look at the situation from Barisic's point of view.

His hand is raised so this is immediately before he begins his run-up. Even from this distance we can see Helander is free at the back of the main pack. 

What else is going on? Well, there's plenty of bodies in the box but we'll come to the who-was-marking-who stuff soon. For now, from Barisic's point of view, there's one other key thing to note: Joe Aribo and David Turnbull in the middle of matters just outside the six-yard box.

Celtic Way:

Why is this important? Because, as Barisic runs up to take the corner, Aribo darts towards the front post, taking Turnbull with him in the process and leaving space for the Rangers players loitering behind to try to burst into. In turn, this makes it easier for the still-unmarked Helander to stride into his jump unopposed a lot closer to goal.

Marking issues

Celtic Way:

Now we flip round as the ball is in the air and Helander is on the move. I've marked the key players to look out for by name but there's more going on here as well.

As mentioned, Aribo has led Turnbull away from the edge of the six-yard area and the movement of Leon Balogun, Connor Goldson and Alfredo Morelos towards that part of the box is creating space for Helander to charge into. 

Balogun is a curious one. As you can see from the freeze-frame, both Anthony Ralston and Welsh are in his vicinity and the natural inclination is to question why one of them hasn't switched on to Helander. There's no easy answer to this; it's likely a combination of a communication breakdown and being sucked into thinking the danger lay elsewhere.

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It is also worth noting that Starfelt's positioning here does not look too clever regardless. Giving the Swede the benefit of the doubt there's every chance he has, at this late stage in proceedings, clocked the danger Helander's freedom poses and is caught between trying to guard Goldson and disrupting his international team-mate's leap.

Indeed, the main image at the top of this article perhaps encapsulates this. Starfelt is the closest Celt to Helander when he heads it in but has also refused to let go of Goldson just in case.

Here it is zoomed out, showing Christie still has Morelos but no other Celtic player has even entered the frame (except keeper Joe Hart in the background, of course):

Celtic Way:

Past informs present

But who should have been there? 

The glib answer is that it doesn't matter, because nobody was. Nonetheless, patterns emerge within the course of each game and in this one we have the benefit of there having been corners taken before the one from which Helander scored.

In this respect, the way Celtic were lining up for defensive corners suggests Welsh had been tasked with picking up Helander that afternoon.

Celtic Way:

On the occasion in the above freezeframe, Ralston is touch-tight to Balogun while Welsh has Helander, Christie has Morelos and, if you look in the background, Turnbull is once again with Aribo. In this instance Starfelt has actually allowed Goldson a bit of a run on him - and it is the Rangers captain who wins the header, albeit it comes to nothing. 

As it was, at the corner from which Helander scored Welsh seemed preoccupied with Balgoun along with Ralston.

However, after the ball is delivered Welsh actually leaves Balogun too. Instead, he spins into the space directly in front of Hart and this makes it look like he is guarding Roofe, who at this stage has escaped Josip Juranovic at the back post and is sniffing about for any scraps should Hart keep Helander's header out. 

Celtic Way:

Any other business?

In amongst all this, Celtic's defensive setup has Callum McGregor stationed at the front edge of the six-yard box in case of a poor delivery from Barisic but also has Odsonne Edouard standing just behind his captain.

The striker could be there for his aerial presence but it is a slightly odd position to take up - not on the post, not on a man and in an area that there would have to be a very specific type of delivery to actually come into play. 

Celtic Way:

Addtionally, Liel Abada is occupying an area rather than a man but this, understandably, could easily have been in an effort to utilise his pace on a swift counter-attack in the event of a clearance.

The overriding takeaway, however, is that while it is likely a communication breakdown at the centre of it all on this occasion, there remains a certain fragility about the way Celtic defend set-pieces.

Already this season they have conceded as a result of set-pieces in big games against Hearts (which I broke down at the time) and FC Midtjylland.

Add Rangers to that list and take into account the team from last term conceded 12 times from set-plays - a total behind only Ross County, Kilmarnock and Dundee United - and it becomes less a tale of individual errors and more one about a side repeating the same mistakes again and again.