The Frenchman might be a devoted Arsenal player, as well as their star man at the back.
But his latest appearance on social media saw him posing in a Spurs jersey whilst holding up an Arsenal shirt.
Some dedicated Gooners could not believe what they were seeing, one of their best players in the colours of their biggest rivals.
But while Saliba was sporting a white jersey with Spurs on the front, it was actually the basketball vest for NBA side San Antonio Spurs.
The basketball team have no connection to Tottenham, though that did little to quell some supporters.
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One social media user said: "All along Saliba supports Spurs."
A second wrote: "Why is Saliba wearing a Spurs jersey?"
And another put: "I knew Saliba likes Spurs."
However, the post came about after Saliba posed with international chef Abdou Drame in London for a video shoot for Gainde Conciergerie.
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The company a range of luxurious goods including private jets and custom watches, as well as personal chefs like Drame.
Saliba, as part of the collaboration, posed alongside Drame with an Arsenal shirt with the defender's name on the back, which was also signed by him.
Another fan wrote: "The ONLY time you will ever see Saliba in a Spurs shirt. That's San Antonio Spurs FYI."
Saliba has arguably been one of Arsenal's most important players since breaking into the team last season.
The France international has been a rock at the back for Mikel Arteta, whose side narrowly missed out on the Premier League title last season.
And that was largely down to an injury picked up by Saliba as the Gunners started leaking goals without him in defence.
Former Arsenal star Emmanuel Petit has insisted that the 22-year-old is already challenging Liverpool star Virgil van Dijk for the best centre-back in the Premier League title.
Petit said: "I think William Saliba is one of the best central defenders in the league, if not the best.
"His positioning, tackling and aggressiveness is so impressive and he has improved so much in a short space of time.
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"Van Dijk was the best defender in the league for so long but he is not the best anymore. He has regressed since his injury and he lost that consistency.
"I think the best defenders in the league are Saliba, Manuel Akanji, Ruben Dias and Josko Gvardiol."