My 2c+ opinion is apart from Welsh's and Duffy's deficiencies, that back 3 were also exposed because Celtic (like us) were weak in midfield.
Ntcham was wandering about, then decidely not bothering to run with the first goalscorer Krunic, who ran through an acre of space and got between the 2 CHs to head the first goal. Brown was a passenger rather than the midfield enforcer, as soon he was replaced things improved further.
I think we have the same but different midfield deficiencies which mitigate against us using the 3 at the back, 2 will do with a more solid cm
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