[2][4] He signed his first professional contract with the club in January 2021,[4] and was named on the first team bench for the first time on 13 March 2021 for a 3–0 home win over Stoke City.
[11] He scored in successive fixtures against Luton Town and West Bromwich Albion in November 2021,[11] the former coinciding with his full league debut.
[3] On 1 March 2022, he scored the winning goal in extra time in an FA Cup match against Tottenham Hotspur to take Middlesbrough through to the quarter-finals of the competition.
[17] Coburn impressed during his first ten league appearances for the club, scoring five goals, with manager Joey Barton tipping him to go on to play for England.
[19] Despite going through a goal drought of over two months, he retained the faith of Middlesbrough manager Michael Carrick who challenged him to force himself back into the first-team regularly.