Eredivisie leaders PSV Eindhoven could only draw at FC Groningen on Sunday, while FC Twente beat PEC Zwolle to go third.
Sky Sports understands a host of Europe's top guns are tracking Watford's teenage starlet Xane Zaineddine.
PSV Eindhoven retained their four-point lead in the Eredivisie despite free-scoring wins for their nearest pursuers.
Dinamo Moscow and Salzburg made certain of their places in the Europa League knockout stages, but Inter Milan must wait.
PSV restored their cushion at the top of the Eredivisie after a 5-1 win over Utrecht, as Feyenoord nudged up to third.
Napoli lost 2-0 to Young Boys in Bern in the Europa League on Thursday, as Feyenoord went down 3-1 away to HNK Rijeka.
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