St Johnstone haven’t offered much of an attacking threat in this game so far, but there was an obvious mismatch with Shaun Rooney against Greg Taylor in the air.
Rooney is a good few inches taller so Celtic had to plan for this and ensure Ajer or Duffy picked him up if he drifted into the area for the cross.
Instead they allow Taylor to get pinned against him and there’s only going to be one winner in the air, and Celtic are up against it now:
Pictures from Polsat
Rooney’s ability in the air can’t be a surprise to anyone as he’s scored a few goals in recent games, so Celtic need to communicate more at the back and prevent this from happening again.