Former United striker Saha insists that the Red Devils boss must boost his midfield and defence during the January transfer window.
The 1-0 defeat at the Etihad stadium on Sunday left Manchester United in 10th place in the Premier League table, proving to be the worst start for the Reds in the Premier League history even after spending £150m in the summer transfer window.
However, Saha, who won two Premier League titles, One League Cup and a Champions League medal at the United, believes the winter transfer window is an important one for Louis van Gaal.
“I hope they finish in top four but I can't be sure,” said Louis Saha.
“You could say the issues are at the back but it’s about balance, finding the right midfielder to keep the ball and a defender to be strong at a certain point of the game.
“What [the manager] does in this window this winter will be very important for Manchester United.”