Dias meanwhile has only recently returned to training after seven weeks on the sidelines with a hamstring injury but has still to play after his comeback.
“Kyle no. The other players are better, we will make a decision tomorrow,” the City boss revealed at Tuesday’s pre-match press conference.
“Kyle we don't know yet (how long he will be out). It his ankle. He can't play tomorrow but the rest we don't know.
“Ruben is training really good, but we cannot forget he had seven weeks off and has not played one minute.
“Ruben is intelligent. He is a guy who knows his body.
“It’s good to have three or four central defenders.”
Looking ahead to the visit of the Seagulls, the boss said that he was braced for another tough test from Graham Potter’s side who recorded a fine 1-0 win at Spurs at the weekend.
And he said his and the players’ focus was firmly fixed on seeking to try and secure another vital three points as the race for the Premier League title intensifies with City a point ahead of Liverpool who play Manchester United on Tuesday night.
Pep also confirmed he would be watching the game at Anfield later this evening on TV.
“Every time we play against Brighton (is tough) - I have a lot of admiration for how they play and the results they have got. A good test for us," the boss added.
"The challenge is the same like last two weeks. We are going to play every game like it is a final to get an opportunity to play another one.
“We will fight until the end and try to get results.
“I watch the games as a fan. I will be at home, so of course I want to watch it. I would love United to take points, but it won’t change if we don't do our job in the next games.”