The Sporting CP center-half is wanted by a host of top European clubs.
Per A Bola, the Magpies are continuing to assess his qualities through scouting.
The outlet published a list of scouts that were present for Sporting Lisbon's Taca da Liga game against Porto last week.
Diomande, who is 6'3, is also wanted by other top Premier League clubs.Newcastle may well put in a winter bid to try and steal a march on other teams.
However, Diomande has a £67M minimum release clause that may put him out of reach for the moment.