Arsenal scouts were in the stands for Sporting CP's 2-1 win against Benfica.
The Mirror says the Gunners had several players on their radar for the night.
Sporting defender Ousmane Diomande is a top target for Arsenal, as is teammate and striker Viktor Gyorkeres.
Diomande is seen as cover for Gabriel Magalhaes.
Benfica pair Joao Neves and Antonio Silva are also being tracked by Arsenal.