Tottenham Hotspur reportedly sent scouts to watch Benfica's £85m-rated forward Jota in action against Dinamo Zagreb on Thursday evening.
Spurs boss Mauricio Pochettino is preparing for a big summer in North London after going two windows without strengthening his squad.
The 19-year-old has appeared three times for Benfica's senior side this season, most recently in midweek when playing more than an hour of the 3-0 Europa League win against Zagreb.
Tottenham scouts are said to have been present in the Estadio da Luz stands, while Bayer Leverkusen also had a representative in attendance.
Should the Lilywhites act quickly they can land the highly-rated youngster for £25m, but Benfica are hopeful of increasing that release clause to £75m with talks over a new deal progressing.