Rui Patricio has been linked with a summer move to Arsenal
The Gunners were linked with a £13m swoop earlier this week but Sporting would reject all offers that do not trigger his release clause.
And, according to Portuguese publication Record, Patricio has a €45m (£38m) buyout clause.
Arsenal are looking at their goalkeeper options with Petr Cech now aged 34 and showing signs of decline.
Petr Cech has shown signs of decline this season
David Ospina has struggled for games at Arsenal and could leave this summer
David Ospina looks set to quit north London after growing frustrated at the lack of chances.
The Gunners were also linked with Kasper Schmeichel over the weekend and have been monitoring the progress of Jordan Pickford.
Arsenal dropped out of the top four after their last defeat – away to West Brom – and face Manchester City this Sunday.
The stunning Arsenal XI that could've been
Sun, March 26, 2017
Express Sport brings you the stunning Arsenal XI that could've been …if Arsene Wenger had signed these superstar players
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This is an Arsenal team Arsene Wenger could've had if he'd sighed these players
They are currently in sixth, six points behind Liverpool but with two games in hand.
Defeat to City could see them drop down to seventh with Everton currently only behind them on goal difference.
The Toffees face Liverpool in the Merseyside derby at 12.30pm on Saturday.