The 26 year old is a product of Chelsea’s academy but has not made a first-team appearance for the club.
Having spent plenty of time out on loan in his career, a move to the Millers will be his 8th loan, and with just a season left on his Chelsea deal, he will be looking to impress wherever he ends up.
It's rumoured that Warney is keen to take Blackman on a season long loan.
So far, he has spent time at Bristol Rovers, Sheffield United, Leeds, Middlesbrough, Wycombe, Dutch club Vitesse Arnhem and Swedish side Ostersunds.