The playbook is what players should do in different roles. Those roles can be moved between formations and so the playbook is still being used and has not been 'thrown out''.
Smallbone got some valuable gametime in the under 23s 5-0 win vs Newcastle today so wasn't going to be involved tonight having only just come back from serious injury.
Both Diallo and Stuart Armstrong can be used in central midfield tonight if needed later in the game.
That does not answer the question as a big pile of cash would also be available for him in the summer. So what is the incentive for Saints to sell mid season vs the summer?