Gallagher made his competitive debut in the 1-0 win at Everton on opening weekend but played just one minute off the bench at Goodison Park, while Hudson-Odoi was omitted from the matchday squad despite travelling to Merseyside.
The duo will be hoping to make the bench for Sunday’s London derby at home to Tottenham and Tuchel has urged patience from the fringe players in his squad.
"In general nobody is for sale," Tuchel told reporters. "Nobody is for sale and everybody is for sale.
"It depends on what the player wants, how bad the player wants it, what we think about who is ready to pay a certain amount of money and then maybe everybody is for sale."
Adding about Gallagher, who is receiving loan interest from West Ham, Crystal Palace and Everton, among others, Tuchel said: "Conor fights in central midfield.
"To be honest, it is a very tough fight for him. It seems we only have two places in central midfield. Given the amount of players we have for central midfield, it isn't ideal I agree.
"But we have to do what's best for the squad not just each individual player, so these thoughts are not 100 per cent about the formation. But at the moment, he is absolutely fine.
"I am a huge fan of Conor. He is a fantastic guy and this is what we already knew. In the first weeks of training he has shown how much of a step he has made through having so much playing time, through his personality on the pitch. It is a very, very normal situation and development at the moment that after some fantastic training sessions in the beginning, there is a little dip in his form and freshness which he suffers.
"On top of that, there's a huge competition with N'Golo [Kante], Jorgi[nho] and [Mateo] Kova[cic], who are used to playing with each other. This is also life in a big club like Chelsea, so everything is in its right place.
"We are happy with him. He keeps on fighting and this is what he does. I think he has everything to become a very important player in the next years at Chelsea."
Meanwhile, Hudson-Odoi has loan interest from Borussia Dortmund, Southampton and Leicester. Tuchel had similar words for his winger and urged him to learn from new signing Raheem Sterling.
"Callum is the same," he added. "He had a long-term injury and long-term problems to overcome. That's where he suffered from. I think he still has a way to go to live up to his potential.
"His potential is huge. I think having Raheem in can give him an extra boost to step up and see what's needed in these kinds of positions to reach the levels he can honestly reach. But at the moment, he is our player and he needs to fight, fight, fight. I have nothing more to say."