Ange Postecoglou has said Ruben Amorim will succeed at Manchester United if he is given two years to work at Old Trafford.
Since joining United from Sporting CP in November, only five teams have won fewer Premier League points and he has won just nine of his 20 matches in charge in regulation time.
United have lost seven of their last 11 league games and are 13th ahead of Sunday's trip to Tottenham Hotspur, who lie in 14th place with Postecoglou also under mounting pressure over his position.
"I've got respect for all managers because I know how tough it is," Postecoglou said on Friday.
"I'm sure if you asked Ruben that he would say he was just doing what he was brought in to do. Obviously they've scouted him, they've identified him, the way he plays, the way he goes about his business. You don't just make these appointments because you like the look of someone. You do actually a lot of work and you bring him in with a purpose.
"Now, if anyone believes that anything can change significantly in a short space of time, they're living in an alternative universe that is not based on reality. I'm sure -- who am I to advise anybody -- but if Man United stuck with Ruben for the next two years, they'd see progress, absolutely, because that's how long it takes.
"And if someone can show me somebody who has done it quicker without significant investment, by all means put it across my desk and I'll follow that blueprint. But we know there's a blueprint there.
"I'm sure irrespective of the noise -- I've only literally spoken to Ruben for probably 30 seconds at a game -- I'm sure he's there going: 'I'm going to do what I was brought into do' and that's what he should do."
Speaking at the same time in Manchester, Amorim acknowledged the similarities of two principled managers coming under scrutiny amid calls for a change of approach.
"I am a huge fan of Ange Postecoglou," Amorim said. "He is a good guy, a very good coach. I understand the connection with me and Ange. We have the same problem. In my opinion, and with respect, I am at a bigger club, with bigger pressure, and I think coaches must follow their principles.
"He wants to play football in the right way and that's a good thing. We know when we choose this profession. there are a lot of good things, but you have to feel the pressure when you don't win."
Postecoglou will welcome back goalkeeper Guglielmo Vicario, midfielder James Maddison, and defender Destiny Udogie to his squad as Spurs look to reverse a run of eight defeats from 11 league games which the 59-year-old admitted had taken a toll on him.
"I've been grumpy? Fair enough, too. I've had to do this [speak to media] three times a week, sometimes on zero sleep. Cut me a little bit of slack. I can't be bubbly and cheery all the time.
"Fair to say I appreciated the fact there wasn't a game this week, for sure. I had dinner with my family last night and my boy said 'it seems like you haven't had a game for a while, Dad' It's only been four days but that's the cycle we've all been in, not just me, all the coaches. When you are going at it all the time, you do get into this cycle where it does become a bit of a grind. But you know you have to do it, there is no alternative. I can't not do things that I'm responsible for.
"Having the opportunity of even this, not having to front up two or three times and answer the same kind of questions allows you to take a breath and hopefully I'm back to whatever I was before."
Centre-back duo Micky van de Ven and Cristian Romero are also closing in on a return to action. Postecoglou said Van de Ven has seen specialists to help avoid a repeat of the hamstring injuries that have blighted his career while Romero's quad injury still needs around a fortnight to heal. Dominic Solanke could also recover from a knee injury in a similar timeframe.