Shaw had started five games in a row and was praised by the manager for his consistent form, with Mourinho admitting there were not many better left-backs around.
However, it was felt Young should get the nod at Turf Moor, after serving a three-match suspension, because of his superior experience against resolute opponents and attacking nous stored from previously playing in a wing role.
"I'm really happy with Luke," Mourinho confirmed. "As I said yesterday, I don't need to go to the transfer market to get a left-back because I'm really happy with Luke and with the adaptation of Ashley Young so I'm really happy.
"But I think this match is a very specific one and one that you need the experience of Young and he also projects very well in attack. That's a decision [you make] when you have two players and a good squad, and you can adapt."