The 26-year-old has made 19 Premier League appearances so far this season - eight from off the bench - and, despite not managing to register a goal in the top flight, has forced his way back into Tuchel's first-team reckoning.
The former Crystal Palace loanee hit the headlines when scoring in Chelsea's 2-0 FA Cup semi-final success over Patrick Vieira's men at Wembley recently - but Tuchel thinks he should be offering more.
"He needs to push himself to the limit; he needs to be physical," Tuchel told reporters, ahead of his side's trip to Old Trafford to take on Manchester United in the Premier League on Thursday.
"Had a bit of a shy game against Arsenal, like everyone. A calm first-half against Crystal Palace and stepped up in the second-half physically and with ball recoveries and dribbles.
"Suddenly the crowd was there too. This is what we demand from him.
"He is a calm person. He needs to discover this monster in him and unleash this on a regular basis because it is absolutely necessary."
Loftus-Cheek's career stalled when he suffered a torn Achilles in 2019 but has come back to form in a combination of right wing-back and central midfield roles for the capital giants in recent weeks.
A good end to the season could see the former Academy graduate come back into the England reckoning ahead of the World Cup in Qatar but Tuchel says Loftus-Cheek has to believe he can influence games more.
The German revealed the club have worked on improving his confidence as part of his professional development and hope to see Loftus-Cheek unlock his undoubted talent.
He said: "It is not enough to be just on the pitch. Maybe if you regard his last years, it may seem good because he is a regular but this is not enough. We cannot let him think it is enough, he needs to constantly push himself.
"We try every day and are quite successful given his development. He needs to understand how much potential he has and unleash this physical capacity on the daily.
"In training he cannot let loose. He needs to be under pressure and play every game like a cup final."