After drawing 1-1 with Uruguay in a friendly on Friday, eight players left the camp due to health and injury issues.
Goalkeeper Aaron Ramsdale, defender Fikayo Tomori and striker Dominic Calvert-Lewin were among those to leave. Defender John Stones returned to Manchester City after sustaining an injury prior to Friday's match, while Adam Wharton of Crystal Palace and Arsenal winger Noni Madueke were injured during the game.
Madueke's Arsenal teammates Declan Rice and Bukayo Saka have also returned to the North London club.
"Disappointed but not with the players, with the fact we want to have everyone in good spirits and health," Tuchel told reporters.
"It's the reality of the end of the season and the end of March, the reality of having players in European matches and more than just one competition with all the cups going on.
"We have players in camp that have already played more minutes than last season, so there is some concern. The players needed and deserved the mental break from football. We could see the energy with which they came back into camp and to reconnect now in the new environment.
"We want them to perform in their clubs, but the reality is it's our last camp before we leave to America, so we want to reconnect to our principles. It's disappointing, but I'm not upset with the players; I'm not angry.
"I got the feeling that everyone was desperate to come. Some of the injured players even stayed to do their treatment, which shows they want to be around the group. No one left straight away, it's a good spirit, and that's how it should be."
'We have time'
Following the Japan friendly on Tuesday, England will face Costa Rica next month as preparations intensify for the World Cup, co-hosted by the USA, Canada and Mexico starting on June 11th.
Tuchel was asked how England compare with other teams such as France.
"I don't know. You cannot compare, you saw our line-up and opponent, it's just March," the former Chelsea and Bayern Munich manager said.
"We are happy with the way we have done our camp until now. I know it wasn't the nicest watch, but I know we played against a well-coached side and best possible line-up of Uruguay."