A move for Ronaldo was considered after the Manchester United forward was offered to Chelsea co-owner Todd Boehly when he met the player’s agent Jorge Mendes in Portugal last month.
But Tuchel has told Boehly he does not want the Portuguese at Stamford Bridge and Chelsea have decided not to pursue a move for the 37-year-old.
Sterling, who completed his £47.5million move from Manchester City last night, can play both out wide and as a central striker. Kai Havertz was used through the middle last season.
Instead, Tuchel wants Chelsea to focus on signing three new defenders.
Kalidou Koulibaly is due to join up with the Chelsea squad on their pre-season tour of the United States in the next 24 hours as he closes in on a £33m move from Napoli.
The 31-year-old Senegal international has agreed a four-year contract and underwent a medical in London.
Koulibaly could be followed into Stamford Bridge by Nathan Ake. The Blues have agreed a deal in principle to sign Netherlands international Ake for around £45m but are waiting for City to sign a replacement before they give the 27-year-old the green light to leave.
Chelsea are also targeting a move for Paris Saint-Germain centre-back Presnel Kimpembe, though the defender will need some convincing.