Ole Gunnar Solskjaer admitted Paul Pogba was only fit enough for a spot on the Manchester United bench for the trip to Newcastle.
The Red Devils ran out 4-1 winners at St James' Park, with three late goals breaking the stalemate after Harry Maguire equalised following Luke Shaw's early own goal.
Pogba - who had started each of United's previous three Premier League games - was called on in the 69th minute, replacing Fred in midfield with the score 1-1.
The 27-year-old's introduction helped the Red Devils take the lead in the 86th minute through Bruno Fernandes, before Aaron Wan-Bissaka and Marcus Rashford secured the three points.
After the match, Solskjaer confirmed Pogba returned from international duty with a number of complaints which meant he was not able to start the game.
The United boss said: "Paul had hip and back problems when he was away with France, so it wasn't right to start him."
Pogba was involved in all three of France's fixtures during the international break. He came off the bench in the 7-1 friendly win over Ukraine and the 2-1 Nations League victory over Croatia, and started the 0-0 draw with Portugal.
Solskjaer will be hoping he returns to full fitness in time for a challenging run of fixtures which sees United face Paris Saint-Germain, Chelsea, RB Leipzig and Arsenal within the space of a fortnight.
Should Pogba return to the line-up once fully fit, or should Solskjaer continue with Fred and Scott McTominay in midfield? Have your say here.
"We have got big games coming up," Solskjaer added. "Everyone has to perform when they come on. I am delighted for him."
United kick off their Champions League campaign with a trip to Parc des Princes on Tuesday night before they host Leipzig at Old Trafford eight days later.
Group H is rounded out with Turkish champions Istanbul Basaksehir, whom United face twice in November.
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