McCarthy was unemployed for four months after being fired by AmaZulu FC as the club's head coach in March 2022.
The Cape Town-born tactician returned to professional football when he joined United - heading back to the Premier League, having turned out for Blackburn Rovers and West Ham United in the English top flight during his illustrious playing career.
The Red Devils' official website explained that McCarthy 'will specialise in coaching attacking plays and positioning'. The retired hitman thrived in this role as he was credited for Marcus Rashford's improved form in front of goal and washailed by Ten Hag.
Rashford scored 30 goals across all competitions for the first time in his career and the England international won more Premier League Player of the Month awards (three) than any other player during the campaign.
United's improvement in front of goal with McCarthy overseeing the team's finishing drills contributed to the team clinching the Carabao Cup, reaching the FA Cup final, and securing a top-four finish in the Premier League.