Hackney came off the bench in Boro's play-off final clash against Hull City after replacing Southampton, who were booted out by the EFL due to the spygate saga.
But their hearts were broken when Oli McBurnie scored a 95th-minute winner to send the Tigers into the Premier League, while Kim Hellberg and his staff had to accept that not gaining promotion would result in Hackney's departure.
The 23-year-old has been linked with numerous Premier League clubs in the past few seasons, and with only one year left on his contract, now is the right time to sell.
An emerging report from The Telegraph even states that Hackney is available for a bargain price of £10 million, less than a year after almost joining Ipswich Town for £20 million.
Everton are long-term admirers of the Championship Player of the Season and want to make the Englishman their first summer signing, while Tottenham, Leeds United, Crystal Palace, and Brighton are all interested.