Friend, 27, has been in impressive form for Boro this season, making 26 Championship starts on a backline which has conceded just 18 goals – the best defensive record in the division.
The former Doncaster Rovers man penned a new four-year deal at the Riverside Stadium in August, but his recent performances have only served to increase reported interest in his signature.
Palace and West Brom are now considering an approach during the closing week of the transfer window, while Queens Park Rangers are also among the interested parties, despite their tight financial situation making a deal unlikely.
Capable of filling in at centre-back, Friend has made 110 total appearances for Boro since arriving from Doncaster in 2012, and was voted the club’s Player of the Season last term.
With Aitor Karanka’s side sitting in second place in the Championship table, it’s unlikely he will be allowed to leave Teesside this month without a sizeable bid coming in, and it remains to be seen what kind of fee Premier League clubs are willing to fork over.