Guardiola: Kalvin Phillips 'ready' to start for Man City
Phillips signed for the Premier League champions in July but underwent shoulder surgery in September and only made four substitute appearances for City prior to the World Cup.
Following the tournament in Qatar, the 27-year-old was described by Guardiola as "overweight" and not "in the condition to do training sessions and to play".
He has subsequently come off the bench twice against Chelsea as City beat them 1-0 away in the Premier League last week and then 4-0 at home in the FA Cup on Sunday.
Guardiola was asked at his pre-match press conference whether Phillips would start against Southampton on Wednesday.
"He's always ready," said the City boss.
"Of course I think (it takes) a little bit of time for some aspects but he's ready and we are delighted about that."
Guardiola added: "I think he's an intelligent player - normally holding midfielders are so clever and intelligent - and has an incredible work ethic in the training sessions.
"He was educated at Leeds with Marcelo Bielsa, with Jesse Marsch (as well) but especially Marcelo, the fact of the commitment every training session, every game. So I don't have doubts about that - but of course there are patterns and movements, things that need time and games and games."
Guardiola has won the League Cup four times, making him the joint record-holder alongside Brian Clough, Alex Ferguson and Jose Mourinho.
He was keen to stress that it would not mean anything to him to become the manager with the most successes, saying: "I don't know if the reason why you are the best is for the trophies you won.
"(And) I said many times, we won a lot in a short period of time but in my case I was at three fantastic clubs (Barcelona, Bayern Munich and City), and I never forget the success belongs to the players, the structure, the hierarchy, the foundations of the organisation."