Pep Guardiola believes Mo Salah must reproduce his form of last season over "eight or nine years" to justify comparisons to Sergio Aguero.
Salah scored 32 goals in 36 Premier League games in his debut Liverpool season - beating Aguero, who got 21 goals, to the Golden Boot.
However, Salah's total goals scored in the English top fight (37) trails City's all-time leading scorer's (148) by 111.
"He (Salah) is younger and it was his first year back in England since his time at Chelsea, so we will see in the future," said Guardiola, talking ahead of City's visit to Liverpool in the Premier League on Sunday.
"But a guy who has the quality to score 50 goals in a season always has that quality. But football is all about ups and downs.
"Salah remains an excellent player and will score goals in the future. When you are in there scenting goals sometimes this happens.
"Sergio has scored a lot of goals but there were periods when he didn't score goals.
"How many years has Sergio scored all those goals, eight or nine years? For Salah it was the first one so we will see in seven or eight years."
Guardiola insists he has no concerns about starting Raheem Sterling at former club Liverpool on Sunday.
Sterling has received hostile receptions and struggled in games at Anfield since leaving Liverpool Manchester for City in 2015.
Despite being one of City's key players throughout last season, the England international was used only as a second-half substitute when the sides met on Merseyside in the Champions League quarter-finals in April.
But Guardiola claims that was a tactical decision and he is not shielding the 23-year-old, who he expects will learn to cope with the challenges of returning to his old stomping ground.
Guardiola said: "The reason why last time he didn't play was for other reasons: tactical. What I wanted to do was have Kyle Walker on the right side attacking more than him. That was the plan. Sometimes it works, sometimes not.
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"I don't think about that (crowd reaction). Even if that happens - maybe it affects him, maybe not - but being so young, he has to learn about that.
"When he has been a player for us for a long time, and hopefully it will be for a long time, sooner or later he will go many times to Anfield.
"He grew up there, he has a good memories about his period there. Of course the Liverpool fans want (him) to play bad, and he has played bad but he wants to play good. Normally I don't do it for that reason."