Not sure if Arteta is the kind of guy to try an "experiment" during a title challenge. Anyway, I will humour you. Tomiyasu's run at left back ended after 4 games after picking up an injury in the Europa League. Did Arteta opt for Tierney for the next league game? nope, he experimented with a half fit Zinchenko. If Zinchnko picks up another injury and Ben White is fit, my money is on Tomiyasu starting at left back again. He has started more games LB than Tierney since October and the "experiment" worked (3 wins 1 draw).