The England head coach told the Real Madrid full-back he has "no choice" but to learn to defend if he wants to remain part of his long-term plans.
Real Madrid fullback Alexander-Arnold had been left out of England's World Cup squad but has now been given an olive branch for the Nations League campaign, in stark contrast to the treatment of Manchester United centre-half Maguire, who was also axed for the summer tournament and reacted publicly to his omission.
Asked whether Alexander-Arnold must now defend as part of his England role, Tuchel was direct.
"He has to, he has to. It's necessary. My conviction is that he will but he has no choice," Tuchel said. "I know what he is capable of. I know about his talent. I know what he is saying. That he is desperate to play for England and he will fight for his shirt. So here we are.
"He is in camp and he has the chance. It's a long camp and it's a good moment to show up."
Tuchel had not spoken to Alexander-Arnold personally before recalling him this time, but had noted the player's public comments about wanting to return to the fold.
"I spoke to him before the World Cup and told him my decision and this time it was the good news. He heard the good news over the nomination," Tuchel said. The recall also comes with Ben White and Reece James missing out through injury.
Maguire, whose mother said she was "absolutely disgusted" by his exclusion from the World Cup squad over the summer, received a far cooler response. Tuchel, who called up Everton's Jarrad Branthwaite ahead of the Manchester United defender, stopped short of shutting the door completely but left little doubt that a recall remains highly unlikely.
Asked whether the reaction to Maguire's omission had made him harder to select, Tuchel did not hold back.
"It doesn't help. It does not help," he said. "I will not hold it against him for the rest of his life because I'm not that type of person. I can forget easily and quickly, but I didn't like it and it doesn't help."