[11] Three weeks later, whiplash suffered in a car accident by second-choice goalkeeper Jack Bonham saw Balcombe win his maiden first team call up for a West London derby with Fulham.
[15] He received his only first team call up of the season for a FA Cup third round match versus Notts County on 6 January 2018, in which he remained an unused substitute.
[19] After regaining fitness, he won his first senior Brentford call up of the 2018–19 season for an FA Cup third round match versus Oxford United on 5 January 2019.
[25] Balcombe returned fit for the 2020–21 pre-season and owing to the departure of Patrik Gunnarsson on loan,[26][27] he served as third-choice goalkeeper behind David Raya and Luke Daniels.
[2] Balcombe signed a new 4+1⁄2-year contract on 6 January 2021 and later that day, he joined League One club Doncaster Rovers on loan until the end of the 2020–21 season.
[36] Unable to dislodge first-choice goalkeeper Ben Garratt, he made just three EFL Trophy appearances before the termination of the loan on 4 January 2022.
[38] Initially appearing only in FA Trophy matches, Balcombe displaced first-choice goalkeeper Mark Cousins in the league lineup in March 2022.
[41] He started in the club's opening 2022–23 fixture versus Carlisle United later that day, but was substituted due to injury at half-time during the 1–0 defeat.
[43][47] Following involvement in Brentford's 2023–24 pre-season matchday squads,[48][49] Balcombe began the regular season as third-choice goalkeeper, behind new signing Mark Flekken and the departed David Raya's deputy Thomas Strakosha.
[50][51] On 26 August 2023, Balcombe was included in a competitive matchday squad for the first time since September 2020, when he remained an unused substitute during a 1–1 Premier League draw with Crystal Palace.
[2] Three days later, he made his competitive debut for the club with a start in a EFL Cup second round match versus Newport County.