Broja is reportedly attracting interest from the likes of West Ham United and Newcastle United after an impressive loan stint at Southampton last season.
The 20-year-old Albania international is back at Stamford Bridge to stake a claim for first team football but suffered a setback when he suffered an injury in training this week.
Broja scored nine goals in 38 games for Southampton last season.
Responding to interest in Broja from Chelsea's pre-season camp in the United States, Tuchel said: "Armando is our player first of all, and we have at the moment no interest in selling him."
"He is here to make an impression after he was on loan in Southampton. It's good there's interest; it shows us that there is a talent and potential.
"Armando is in the position to impress and to become a Chelsea player. When? Nobody knows, but hopefully as soon as possible.
"He got injured. It's never nice because the young players should normally make an impression during pre-season from the very first minute. Now we have a little delay in that."
Broja has been at Chelsea since the age of nine and has come through the youth ranks to reach this far.
He made his senior debut for Chelsea in a 4-0 Premier League win over Everton in the 2019/2020 season but that remains his only competitive appearance for the Blues.
Broja signed a new five-year contract at Chelsea last summer.
