The Portuguese defender missed all of March and will not feature in any of the upcoming three games at least.
The boss has also revealed the frustration at Cole Palmer’s stop/start progress as he recovers from a foot problem.
On Dias, Pep said: “The doctor said the position when he got injured is so risky, we have to be careful.
“They tell me (it could be) four to six weeks, but it’s much better to go to six than four.
“If you break again it can be a long time. We won’t take a risk him, when he’s fit he’ll be back.
“If he went down he’d be out for the season. The most important thing is I wouldn’t pick a player to play when he’s not fit or ready, if the doctors and himself on the pitch prove in training sessions and say I’m ready and after he would be ready, but I won’t take the risk if the doctors say not yet.
“We have to wait until he is doing the process perfectly.
“I spoke with him before I came here, he’s happy but muscular injuries are always a process, in the position it’s four or six weeks, you can massage or eat or sleep better and it’s still 4 to 6 weeks, nothing is going to change.
“You have to wait, it’s a question of time, hopefully we can help him to enjoy the last parts of the season in the competitions. This is our job.”
Cole Palmer has also missed several weeks, punctuating his continued impressive progress with the first team.
Guardiola says the youngster still has issues that are keeping him side-lined with no immediate prospect of a return
“He had two comebacks, but after it’s still a process, he’s not clear,” said Pep.
“It’s still a bit painful and we have to take a decision on what we have to do.
“He made the FA Cup game (against Swindon) and was incredible and since then, he’s been training two or three days then after has to take three days off.
“We will have to take the decision with what we have to do. It’s a long time where he can’t make a step forward to come back.
“He trained two days ago and felt good but then yesterday and today he could not train.”