*Club domestic league appearances and goals, correct as of 11:33, 16 November 2024 (UTC) ‡ National team caps and goals, correct as of 04:56, 9 September 2023 (UTC)
As a youngster, Johnson had various internships and trials with football clubs, firstly with Queens Park Rangers before heading off to the likes of Tottenham Hotspur, Crawley Town and Oxford United, but failed to secure permanent terms.[1] After a subsequent break from football, Johnson returned at the age of seventeen to play for The Harrow Club at youth level.[1] During his time with them, Johnson played in a friendly against YouTube team Rising Ballers; who subsequently signed the forward.[1][2] He would eventually leave the club, prior to joining Combined Counties Football League side Kensington & Ealing Borough.[1]
After making five appearances for the semi-professional outfit, Johnson joined Chelsea on trial.[1] He earned the possibility of a contract after featuring in Premier League 2 against Brighton & Hove Albion, but was unable to sign due to Chelsea's ongoing transfer ban.[3][1] Johnson secured a trial with Dutch team FC Volendam in mid-2019.[1][4] He was given a professional deal soon after, having appeared in an exhibition match versus VPV Purmersteijn.[1][5] He made his pro debut on 23 August 2019 during a 3–0 loss away to De Graafschap, as he came off the bench to replace Nick Doodeman after seventy-nine minutes.[3]
Johnson scored his first FC Volendam league goal on 13 September, netting in a home draw against FC Dordrecht.[3]
His contract with Volendam ended in the summer of 2022[6] but he reappeared for the club's second team in October 2022 playing in the Tweede Divisie. He also appeared as a late substitute in the last two games of the season for the first team, which meant his debut in the Dutch Eredivisie.