Boro battle for Dutch star
The 31-year-old has been told by Barcelona he is free to leave Camp Nou - which has alerted a number of teams to his availability.
Skysports.com has now learnt that both Boro and Valencia have a serious interest in the defender.
Boro want Reiziger as a right back, they are short of cover in that department and are looking elsewhere after deciding against a move for Leeds' Danny Mills - who spent last season on loan at the club.
Valencia are keen to bolster their defence in general and see Reiziger as the perfect solution - as he can also play in central defence.
The Teessiders are also considering Mario Melchiot, but the Chelsea man - available on a Bosman transfer - has a number of options and may opt to move abroad.
Both clubs are now awaiting a response from Reiziger's camp, although other clubs could yet lodge their interest over the coming weeks.