The Belgian pair lined up together for their national side at this summer's World Cup, giving Manchester United's recruitment staff a close look at how the two midfielders complement one another.
United missed out on several of their higher-profile midfield targets earlier in the window and appear to be shifting their approach towards a shrewder addition rather than pursuing another marquee name.
Raskin, 25, has been a mainstay for Rangers since joining from Standard Liège in January 2023 for a reported £1.5m fee, going on to make well over 100 appearances for the Ibrox club and establishing himself as a regular for Belgium over the past year.
Rangers are believed to value the midfielder at around £20m-£25m, reflecting his importance to Derek McInnes's side and the continued rise in his transfer value since his move from Belgium.
The Scottish giants, who open their Premiership campaign away at Dundee United on 31 July, would face a significant rebuilding job in central midfield should they lose their key performer this summer, though they are understood to be prepared to do business at the right price given the level of interest circling the player.
Raskin's stock has risen sharply over the past twelve months, with his performances for club and country making him a target for several clubs across Europe, including reported interest from Serie A and other Premier League sides at various points during the window.
He made his senior Belgium debut last year and has since become a regular fixture in the squad, featuring at this summer's World Cup as his country's midfield options continued to develop around him.
Should United follow through on their interest, it would represent a lower-cost alternative to the high-profile midfielders they have been repeatedly linked with throughout the summer, fitting the more pragmatic recruitment strategy the club appears to be pursuing as the transfer window enters its final weeks.