Ruben Amorim will leave Sporting for Manchester United in this month's international break
Sporting boss Ruben Amorim says Manchester United fans may think "the new Alex Ferguson has arrived" if his team beat Manchester City on Tuesday.
Amorim, 39, has two more games as Sporting head coach before taking over at Old Trafford - including the Champions League match against his new team's rivals.
"If the result is very negative, expectations will drop and I don't think that's a bad starting point, when you begin at Manchester United," he said.
"If we win they'll think the new Alex Ferguson has arrived, which is very difficult to maintain.
"I'm fully aware that I'm going to be judged as a manager on this game, and only on this game, and I realise what [people] can take from this depending on the result."
Ferguson won 38 trophies during 26 years as Manchester United boss before retiring in 2013. He is leaving his role as club ambassador at the end of the season.
Sporting have won 14 of their past 15 games in all competitions, only losing the Portuguese Super Cup this season.
Both City and Sporting are on seven points from three Champions League games so far.
In 2022 City beat Sporting 5-0 on aggregate in the last 16 of the competition.
"I feel like I'm a better coach [now]," said Amorim. "Unfortunately what I feel is that Pep Guardiola has also become an even better coach, so the gap remains.
"[City have] the best team in the world and the best coach in the world."
City's Portugal midfielder Bernardo Silva was team-mates with Amorim at Benfica in 2013-14.
"He always showed he could read the game because he played different positions - as a defender, on the left, as a midfield player," said Silva.
"When he arrived Sporting hadn't been champions for 20 years. He changed the playing paradigm of Sporting. They are the best team in Portugal by far.
"He will be a rival but I am glad someone else from Portugal is in the best league in the world.
"When Ruben becomes coach of Man Utd, we will worry about that then. Right now we want three points to get to the top eight."
Manchester City come into the game after back-to-back 2-1 defeats, by Tottenham in the Carabao Cup and Bournemouth in the Premier League.
But manager Pep Guardiola is not worried.
"We lost one game in the Premier League. Maybe we will lose against Brighton and Tottenham [in the next two league games] but we lost one game and we are two points behind a top-class team in Liverpool," he said.
"We have done decent in the Champions League. I know people expect us to win 38 games 5-0 and win the Treble every season, because this is our standards, but this will not happen.
"It's more difficult because we have a lot of absences. There are seasons where to win the Treble everything has to be on the same page - no injuries, good momentum, opponents drop points at the right time.
"This is not possible because Oscar [Bobb] was the best player in pre-season and we miss him a lot, Jack [Grealish] is still not fit and Rodri, the best player in the world, is not here for the rest of the season."
Watch highlights of every Champions League game from 22:00 on Wednesday on BBC iPlayer and the BBC Sport website and app.
There will also be a Champions League Match of the Day on BBC One on Wednesday, from 22:40 to 00:00.
