Spurs have yet to score in four Premier League matches this season and have collected only two points, increasing scrutiny on De Zerbi after the club signed 10 new players in the close season.
The weekend's 0-0 draw against Everton extended Tottenham's goal drought to four league matches, the longest scoreless start to a season in the club's history.
Richarlison, meanwhile, was left out of Tottenham's Premier League squad and also failed to secure a late transfer.
"The situation is the same," De Zerbi told reporters on Monday.
"At the start of this season I spoke to him many times to convince him (Richarlison) to stay and he didn't want to. I can't go every day to pray for him to stay."
The decision leaves Tottenham without a player who has scored four goals in seven appearances against Liverpool.
However, De Zerbi backed his reshaped attack to improve as players become fitter and more accustomed to his system.
Striker Dominic Solanke, summer arrivals Savio and Omar Marmoush, as well as Mohammed Kudus, Conor Gallagher, and Mathys Tel, have yet to make a significant attacking impact in the opening weeks of the season.
"Solanke is a good player and I'm sure he has to improve his physical condition and to stay positive, he's able to score many goals with us," De Zerbi said.
"Savio and Marmoush didn't play many games in Manchester City because they were not the protagonists. Here the situation is different, they have more responsibility, they have to adapt and understand the situation is changing, but in terms of quality both players are very good."
Tottenham will be without record signing Sandro Tonali, who has picked up a knock, De Zerbi confirmed, adding forward Dejan Kulusevski and defender Pedro Porro also remain sidelined.
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