Scouts from Manchester United, Tottenham and Leicester City were present for Benfica's Champions League qualifier against PSV.
The Portuguese giants claimed a 2-1 victory in the first leg of the tie, with the winner headed to the group stages.
A Bola in Portugal has reported that a number of big clubs were watching proceedings in the stands.
Along with the aforementioned clubs, scouts from Juventus, Roma, Bayern Munich, Atalanta and Rennes were also in attendance at Estadio da Luz.
The report does not specify the players being assessed.
However, PSV winger Noni Madueke has been attracting a number of clubs this summer, including Leicester and Spurs.
Benfica striker Carlos Vinicius, who spent last season at Spurs, was also an attraction for those onlookers.