Ibrahimovic will play for the third time in seven days as Manchester United take on West Brom and Jose Mourinho admitted that he simply couldn't leave the Swede out of the starting XI.
"It is impossible [to drop him],' Mourinho said. 'But West Brom is the last effort and then they will have a week without football. And that is a week my players need, especially a guy like Zlatan.
"Sometimes in other positions you can hide yourself a little more, protect yourself. As a striker he is in one of the impossible positions where you can't hide.
"He is phenomenal, play again and then one week to rest. I am not surprised at all by him. I knew from the physical point of view he could cope but obviously he cannot play 60 matches.
"But as our target striker we can see he is the only one. And the way we normally play we need him".
Ibrahimovic has scored 14 goals in all competitions this season and will be looking to add to his tally against the Baggies on Saturday.