Levein brought on Miller and Chris Iwelumo for Mackie and Caldwell as the Scotland coach had to abandon his defensiveformation for a more adventurous 4-4-2.
The Italian giants travelled to London with a slender 2-1 lead and Mourinho ditched his normally defensive tactics with an attacking formation that reaped dividends.
They were transformed to the more secure and positive thinking side back on their Lancashire territory, but had initially found the defensive 4-5-1 formation of a miserly Birmingham difficult to play through.
Such has been the emphasis on that aspect of Wales' play under Gatland and Shaun Edwards that even in attack Wales' formation has recently mirrored a defensive pattern.
Unfortunately, Innes injured himself in making the clearance and had to be replaced by Allan Johnston, as St Mirren manager Gus MacPherson, lacking defensive options, was forced into a more offensive formation.