Sancho was missing from the matchday squad in Manchester United’s 3-1 defeat against Arsenal at the Emirates Stadium.
Manchester United manager Erik ten Hag explained after the game that the winger did not perform well enough in training to make the squad.
Sancho directly contradicted his manager and insisted that the Dutchman was making him a scapegoat.
It has lit a fire around Manchester United, who have made a slow start to their season, losing two of their opening four Premier League games.
Fjortoft insisted that Sancho’s outburst was poorly advised and admitted that it was the wrong decision from the Manchester United winger.
He insisted that Ten Hag must have tried to sort out the issue behind the scenes and while he admitted that the player has a right to voice his opinion, he cannot go against the manager in a public manner.
The former striker took to Twitter and wrote: “I do not think Sancho has received good advice here.
“I presume Ten Hag has tried to solve this internally and then he hopes this can get the right reaction.
“Yes! A player has a right to have an opinion. But the boss is the boss.”
Sancho’s career at Manchester United has failed to take flight since making a big-money move to Old Trafford from Borussia Dortmund.