The France international, who has started 22 of the Lilywhites' 23 Premier League outings this term, missed training on Friday afternoon.
Spurs boss Pochettino is unsure whether he will be able to call upon Lloris at St Mary's Stadium, with back-up stopper Michel Vorm standing by if required.
Asked about the Frenchman's chances of playing this weekend, Pochettino told reporters: "I don't know. It's difficult to say. We need to wait today and tomorrow and then tomorrow we'll assess him if he's available or not. I think it's flu or a virus."
Tottenham have the fifth-best defensive record in the English top flight this season, conceding 21 goals in total.