The 18 year-old Brazilian has burst onto the scene this season, emerging as one of the brightest prospects in Europe.
Okdiario says his breakthrough hasn't gone unnoticed at Real Madrid, where they're now posting scouts to London to monitor his performances.
And it's suggested Real have been encouraged by recent comments made by Martinelli complaining that Arsenal had blocked him from accepting an U23 call-up by Brazil.
Such tension will be used by Real to drive a wedge between the two parties should it become a major issue for the player.
Martinelli is currently on £10,000-a-week at Arsenal to 2024, though the board are keen to treble those terms as a reward for his success this season.