The Manchester City star was one of several big names omitted from the Three Lions' squad alongside Cole Palmer, Harry Maguire and Trent Alexander-Arnold.
Speaking to talkSPORT, the former Chelsea manager admitted uncertainty over Foden’s best position played a major role in the decision, with the England boss opting for players better suited to his tactical setup.
“With Phil, it’s a little bit different, he was excellent in camp for us…not only in training but also out of it," Tuchel said.
“It hurt me a lot actually to tell him this decision. I could see in his reaction how much it would have meant for him to come.
“But he lost momentum in a crucial part of the season, especially in the last half of the season…we could see glimpses here or there, but not enough evidence.
“I was unsure in the end what position he is. Is it a 10, is it a false 9, is it maybe more of a Bernardo Silva role in the future as an 8?
“It’s maybe not on the wing anymore, so it doesn’t make sense to me to bring players and maybe play them out of position…to have them in camp it would make them uncomfortable, unhappy, so the decisions have to be made.”