“Let’s not even go into how a club like Arsenal, whose owners wanted them in the closed-shop European Super League, finds itself without a back-up left back,” Keown added.
“Villarreal boss Unai Emery identified Xhaka at left-back and Dani Ceballos on the left of a midfield two as the vulnerable area in Arteta’s side on Thursday.
“Emery showed his experience against a team he knew well, while Arteta showed his inexperience.”
With Arsenal’s hopes of salavaging their season now resting on next Thursday’s semi-final second leg against the Yellow Submarine, Keown said Saka must play at left-back if Tierney remains unavailable.
“If Tierney is fit, he walks into the team for that all-or-nothing second leg,” said the former centre-half. “If not, Saka must play at left back, a position where has excelled previously for club and country.
“If Arteta sticks with 4-2-3-1, Xhaka can then go back alongside Thomas Partey in midfield, where he has been much improved this season.”