He kept pressing, growing in influence as Anderlecht exhausted, until the pressure he continued to provide at No.10 paved the way for Rashford to score a dramatic late victor to send United through to the semis.
But the 3-2 aggregate success came at a price, with Ibrahimovic and Rojo both seemingly set for extended spells on the sideline after being taken off.
United's record goalscorer Wayne Rooney made his return against Anderlecht, taking his place on the bench after missing four games with an ankle injury, but Mourinho suggested the club captain is not yet ready to play.
Mourinho last week said the England centre-backs were out until mid-May, but suggested after the Anderlecht win that they need to be "brave".More news: Herrera vows to keep proving his worth
The Manchester United manager said the severity of the injuries is likely to be known in "a couple of days".
United find out their semi-final opponents in Friday's draw, with Ajax, Celta Vigo or Lyon lying in wait.
Both players will be bemused by his comments, with Smalling already having been criticised by the Portuguese for pulling out of a game at Swansea City when he had broken a toe, earlier this season.
"But the news is fairly negative I think".More news: Wounded vet running Boston Marathon carries race partner across finish line
"He could by age, so when you reach a certain level - and he's reached that level for a long time - I don't think it makes sense, but the power is in their hands".
"We can not do miracles".
"But he was not scoring a goal since September and because of his mentality, because of what he gives us, even if he isn't scoring goals I kept relying on him". There are no miracles but with special spirit you can sooner than expected. "So instead of coming mid-May you can come beginning May - this kind of acceleration of the process", he said.
He said: "I'm relieved, relieved, hard game".More news: Lingard: Herrera was key to Chelsea win
"I am exhausted. I imagine the players are more exhausted than me".
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