Partey walked off the pitch while Spurs were hitting Arsenal on the break, with Gunners boss Mikel Arteta seen trying to push him back on the pitch.
He was unable to make up any ground and returned to the touchline, but Souness was more concerned by Xhaka’s inability to spot danger.
Xhaka didn’t occupy the space where Partey had vacated by hobbling off the pitch and a swift counter-attack saw Arteta’s side fall 2-0 down, following Son Heung-Min’s glorious curled opener.
‘Leaders don’t allow that to happen on the football pitch,’ Souness told Sky Sports.
‘Forget he [Partey] walked off. If he’s injured – he’s screaming at people saying, “I’m injured”.
‘If you watch Xhaka there, he leaves Lo Celso and just runs into the box.
‘As a midfield player, as a central midfield player, a holding central midfield player – I don’t know what Xhaka is, he’s been here for six or seven years and I’m not quite sure what he is – the alarm bells are ringing.
‘All the time you’re looking over your shoulder, “Where are we vulnerable?”
Partey – who had returned from injury against Tottenham Hotspurafter a month on the sidelines – was swiftly replaced by Dani Ceballos after the goal.