The England manager also welcomed the prospect of Jude and Jobe Bellingham sharing an international camp for the first time after handing the Borussia Dortmund midfielder his maiden senior call-up.
Tuchel admitted that Arsenal's Eze was fortunate to keep his place, particularly given his lack of regular starts at club level, but pointed to the advantage enjoyed by players who had been part of the previous England camp.
"Phil is always an option because I'm in love with him as a player. What is not to love? If you see the boy train it's just the highest, highest quality. I think he has to be always an option. And he is always an option. It was very close.
"It's also close for Eberechi Eze to keep his place with us. He's not starting for Arsenal. So the advantage was maybe that Morgan Gibbs-White and Eberechi Eze come again into camp.
"The advantage was that they have been in camp. Because they need to fight for it. That's what we want. And Phil is always close."
Foden therefore remains firmly in Tuchel's thinking, but the manager has made clear that previous involvement and the opportunity to impress during international camps carry significant weight.
Mainoo received personal apology
Manchester United midfielder Mainoo was another notable omission, having endured a difficult period after being taken to the World Cup without making a single appearance.
Tuchel revealed that he had personally apologised to the midfielder in front of the England squad and coaching staff, insisting that Mainoo had done nothing wrong.
"He was hugely disappointed from the World Cup, and deservedly so. I said it in front of the team, in front of the staff, I said, 'Sorry that I didn't pick you, you did nothing wrong, that is on me'. He was disappointed.
"I think it cost him a bit of confidence. He was excellent in training and in the way he presented himself through the tournament. So he was never a problem, the way he carried himself."
Tuchel had wanted to include Mainoo in the new international cycle, but the midfielder withdrew from the previous camp through injury. He subsequently struggled for fitness as Manchester United's performances also deteriorated.
"I was desperate to give him the minutes. Desperate to include him in this new start, in Nations League. He pulled out. And he then missed camp, and he missed an excellent camp.
"And then entered a difficult, difficult spell for himself. He was injured now, for a long time. And Man United fell off a cliff a little bit performance-wise. So this is why he suffers from that."
Bellingham brothers share England dream
There was a more celebratory story in the squad announcement, with Jobe Bellingham joining older brother Jude after earning his first senior call-up.
Jude has previously spoken about how much it would mean to represent England alongside his younger brother, describing it as a lifelong ambition. Tuchel said he was aware of that dream and believes having Jude around will help Jobe settle into the senior environment.
"I was aware it was always his dream. I saw Jobe once, I think he watched training very early in my reign. He came over and watched his brother train. We chatted and we said ah it would be nice if one day you are with him Jude.
"I think it will be beautiful for Jude to have his brother close and in camp and to have this experience together. It's a very special moment for them of course."
Tuchel described Jobe as a physically imposing midfielder who is comfortable on the ball and capable of contributing in attacking areas, although he sees him operating in a deeper role for England.
He also acknowledged that comparisons with Jude are inevitable, particularly with both brothers now playing for Borussia Dortmund.
"They look similar, even in their movements, but they are very different players. And let's see – I think they are also different characters, at least that's what I heard."
For the Bellinghams, the call-up represents a significant family milestone. For Tuchel, it is another opportunity to introduce a promising young player while maintaining competition for places throughout his squad.