The 23-year-old sealed a £35 million move to Arsenal from Borussia Monchengladbach this summer and has produced some eye-catching performances for Switzerland at Euro 2016.
The towering midfielder was involved again on Sunday night to help his country earn a 0-0 draw with host nation France and progress into the knockout stages of the competition.
Arsenal fans have been hugely impressed by his three outings in the tournament so far but the former Celtic manager is not completely sold on Xhaka just yet, likening him to the Scottish midfielder.
"I've not been that impressed. He [Xhaka] is alright. He reminds me of Charlie Adam," the 44-year-old told BBC Radio.
He is Arsenal's first and only summer signing so far in a transfer window which has reportedly seen Jamie Vardy snub a move to the Emirates (BBC), after manager Arsene Wenger activated his £20 million buyout clause.
Wenger's side finished 10 points behind champions Leicester City last season and the supporter will definitely be hoping that Xhaka is one of several big signings.
With Jose Mourinho and Pep Guardiola joining Manchester United and Manchester City respectively, it'll be ever so hard to win the title next season and Arsenal, as it stands, certainly need reinforcements.