*Club domestic league appearances and goals, correct as of 23:54, 2 October 2024 (UTC) ‡ National team caps and goals, correct as of 21:49, 25 September 2024 (UTC)
Hackney joined Middlesbrough's academy at under-10 level.[3] Having been part of the Middlesbrough team that reached the under-18 Premier League Cup final in 2019,[6] he signed his first professional contract with the club on 26 June 2019, his 17th birthday.[7][8] Shortly after being named on the first-team bench for a match against Barnsley in November 2019, he was praised by Middlesbrough manager Jonathan Woodgate, with Woodgate claiming "Hayden Hackney deserves to be there because he's been outstanding for the Under-23s".[4]
Hackney made his senior debut for Middlesbrough on 9 January 2021, starting in a 2–1 FA Cup defeat away to Brentford.[9] He made his league debut for the club in the final match of the season as a substitute in a 3–0 defeat to Wycombe Wanderers.[2][10] He signed a new two-year contract with the club later that month.[11]
On 31 August 2021, Hackney joined EFL League Two side Scunthorpe United on loan until January 2022.[12] After playing in the majority of games in the first half of the season, Hackney's loan was extended to last until the end of the season.[13] In the 15th minute of a 2–0 defeat to Exeter City,[14] Hackney was caught spitting at an opponent.[15] The referee did not see this at the time, but after the game, the Football Association confirmed that Hackney had admitted to spitting and was given a six-game suspension.[16][17] He made 31 appearances as Scunthorpe were relegated to the National League.[18]
Hackney's game time at Middlesbrough was limited at the start of the 2022–23 season, but Hackney became a regular starter following the appointment of Michael Carrick as manager in October 2022.[19][20] On 19 October, Hackney scored his first goal for Middlesbrough in a 4–1 win against Wigan Athletic.[21] On 8 December, he signed a contract extension until 2026.[19] Hackney won the Middlesbrough Young Player of the Year Award for the 2022–23 season,[22] having made 38 appearances and scoring 3 goals.[2] Hackney was also nominated for the Championship Young Player of the Season Award for the same season,[23] but lost out to Bristol City's Alex Scott.[24]
On 28 June 2023, Hackney signed a new contract for Middlesbrough, keeping him to the club until the summer of 2027.[25] Hackney captained the club for the first time in a 1–0 home defeat to Aston Villa in the FA Cup on 6 January 2024.[26] On 9 January, he scored the only goal in a 1–0 victory over Chelsea in the first leg of the EFL Cup semi-final.[27]
International career
Hackney represented England at under-15 level.[3] He is also eligible to represent Scotland because his mother was born in Edinburgh. He debuted for the Scotland under-21 team in November 2022.[28][29] In September 2023, he was called up to the England under-21 squad for the first time.[30]