The striker has attracted attention from several Premier League sides in recent times, according to reports.
The Star reports that both Leicester and Crystal Palace also had representatives at the game - which Sporting would go on to lose 1-0 thanks to a goal from Fulham forward Kostas Mitroglou, who is on loan at Benfica - but Spurs have been keeping a keen eye on the player since the 2013 African Cup of Nations, so are supposedly leading the charge for his signature.
While the Algerian is unlikely to have impressed any scouts with his recent form - having not scored in any of his last five appearances in all competitions - he has been hugely impressive this season. His 18 league strikes makes him the division's second highest goalscorer, and has been a key reason why Sporting had topped the table until Saturday's game.
Understandably therefore, it seems likely that the 27-year-old will not come cheap. The Star claims that he has four years left on his current contract so it may take an interested club activating his £23m release clause for a potential deal to be done.
Although the Star suggests that Spurs are maintaining an interest, the fact that they have reportedly been monitoring him for around three years may suggest that a move is unlikely.
His age could certainly be a factor should Tottenham decide against going after the forward. Astonishingly, at 27, he would be one of the oldest players in Mauricio Pochettino's squad if he was to join, which may make the Argentinian reluctant to spend such a figure on a player who is unproven in one of Europe's biggest leagues, especially if the Spurs boss is hoping to build on the success that the team has enjoyed this season.