The United States international has struggled for game-time during an injury-affected campaign, starting just four matches since Tuchel replaced Frank Lampard as head coach in late January.
Pulisic has suffered with lingering hamstring problems ever since sustaining the original injury in last year's FA Cup final defeat to Arsenal.
Pulisic is under contract at Stamford Bridge until 2024 but has been linked with a move away if he continues to be a peripheral figure in west London.
But speaking at a news conference ahead of Saturday's Premier League trip to Crystal Palace, Tuchel pointed to another positive showing as a substitute in Wednesday's Champions League quarterfinal first leg win at Porto, and believes the winger could still be a success at the club.
"Fitness is always important especially for Christian because he has this huge physical impact for us in the amount of sprints and the amount of intensity he can give to a team at then highest level," Tuchel said.
"This is one of his biggest strengths. The other thing is that he need to feel confident and to feel calm, mentally, and then he can be a huge weapon for us.
"He scored in the last game against West Brom, unfortunately the overall game and his need to go off the pitch at half-time clouded the goal and the impact he could have had with that goal.
"But now again he was very close to scoring [against Porto], he had a huge impact from the bench. We have to take care about him, that he hopefully will not be re-injured because I feel him stronger and stronger, more and more self-confident.
"He can be a decisive factor in the next game with his speed, his ability to dribble and his ability to arrive in the box in dangerous situations.
"From balls from the side and crosses, he has the feeling to arrive and to score. So hopefully he can have that impact and it is our job to push him there, to calm his mind that he feels the trust and he feels confident."