Ahh maybe massive was an inappropriate choice of word. But then again I'm not just talking about this match. He's been fairly solid for Ajax in the Champions League, Europa league and the odd dozen Eredivisie matches I've seen in the past couple of seasons. As I stated earlier he won't be a world shattering player but afaik he certainly has a far superior technique compared to Fellaini and is adept at circulating the ball. We also have to keep in mind Spain can unsettle opposition teams with their pressing leading to a few unforced errors or extra touches, especially for the wide-ish role he's playing tonight. Most of the times I've seen him play as a CM for Ajax, especially last season and didn't look out of place at all with their intense possession based system. Keeping that in mind IMO would be a good, more intelligent upgrade on the Belgian (again just as a squad player not a regular starter).