The former Aberdeen, Livingston, and Hearts defender served as Johnson’s right-hand man at Sunderland and Bristol City and is expected to take up the same role in the Capital with the finishing touches being put to his contract ahead of the players returning for pre-season training on June 18.
McAllister, who had a spell at Bristol City as a player, returned to Ashton Gate to coach the Robins’ under-23 side before joining the first team in March 2017 as an assistant head coach alongside Dean Holden.
He left the Championship side in August 2020 and despite interest from National League North side Gloucester City, who offered the Scot the chance to take the reins at Meadow Park, joined up again with Johnson at the Stadium of Light.
The pair were team-mates at Tynecastle and again at Ashton Gate and have been friends for more than 15 years, with Johnson handing his former colleague his first UK coaching role at Bristol City in 2016, following McAllister’s player-coach stint with Kerala Blasters in India during the 2014 season.
Johnson is unlikely to bring in a second member to join his coaching staff with David Gray, who twice served as interim boss last season, remaining on the backroom team.
He expressed a desire to remain at the club and admitted any decision would depend on the new manager – but Johnson is happy for the 34-year-old to continue in his coaching role.
A new goalkeeping coach will be appointed, with the position having been vacant since Jon Busch’s exit and David Mitchell assuming temporary duties for the final few games of the season.