Liverpool smashed their then-transfer record in June, signing the German international from Bundesliga club Bayer Leverkusen for a guaranteed £100 million and up to £16 million in potential bonuses.
Despite showing glimpses of the talent that saw him net 57 goals and give 65 assists in 197 appearances for Leverkusen, Wirtz has struggled to make an immediate impact in his seven Premier League outings.
"If you've been brought in for so much money, people look mainly at goals and assists, but I can tell you he could be on six or seven assists already," Slot told Sky Sports ahead of Sunday's league clash against bitter rivals Manchester United at Anfield.
"He's been a bit unlucky with the finishing when he's given his teammates chances but, in general, for a 22-year-old, it's quite normal that you have to adjust to going to another countr,y let alone going to the Premier League."
Slot also drew parallels between Wirtz's situation and Kevin De Bruyne's early struggles at Chelsea.
De Bruyne's time at Chelsea was underwhelming, but after joining Manchester City in 2015 for £54 million, the Belgian established himself as one of the finest midfielders in Premier League history.
"Maybe I'm now underestimating the best midfielder who has ever played in the Premier League, Kevin De Bruyne, he was 21 or 22 when he went to Chelsea," Slot said.
"Give him (Wirtz) a bit of time, I would say. I'm definitely going to give him a bit of time and in the meantime, he's been unlucky."
Liverpool, on a run of three consecutive defeats across all competitions, sit one point behind league leaders Arsenal.