You can classify three levels of defensive availability for the side:
- Quality selection and we can play an Arteta mad scientist lineup (Saliba, Zinchenko, White, Timber)
- Quality selection but with our more conventional players (Gabriel, Tierney, Tomiyasu)
- Sub-par or jury-rigged selection (Holding, Kiwior, Cedric, Partey, Jorginho et al. in defence)
Arteta's very obsessed with the difference between (1) and (2), but the difference between (2) and (3) was what killed us last season.
I think it's likely Arteta wants to go to market just because in our first two league fixtures he's tried out Tomi and Partey in a bid to keep his mad scientist dreams going, rather than reverting to Gabriel or Tierney who are excellent defenders.
After Timber's unfortunate injury, if Cedric, Holding, Tavares and Tierney all leave as we half predict, the right side of defence is vulnerable to another Tomiyasu issue. If Tomi goes down, we really don't want another injury after that, and we risk fatigue and stress injuries for Saliba and White big time.
Nothing wrong with Tomiyasu as a player. If he were as durable as White he'd be a great asset. He seems to be regarded as slightly less coachable but he might just not have had the chances yet.