Pep Guardiola admits Joe Hart is unhappy at being left out of the Manchester City side.
Guardiola wasted little time in shaking things up at the Etihad Stadium as he dropped the England number one for his first match in charge on Saturday.
Hart had to watch from the bench as Guardiola's new-look City laboured to a 2-1 victory over Sunderland and the surprising and ruthless selection decision is sure to fuel speculation over the 29-year-old's future.
"I'm pretty sure he is not happy," said Guardiola. "All the players who don't play aren't sacked, they're absent. Of course I would not be happy if absent, but now it is 'try again'.
"I am sorry, I have to decide (on the team). We have 28 players. They have to convince me on the pitch."
Hart generally had an excellent 2015-16 season and has been a key component of City's successes in recent years.
But he had a difficult time on England duty at Euro 2016 and City have been linked with other goalkeepers since the arrival of Guardiola in the summer.
Yet while Guardiola has confirmed his decision was based on his preference for goalkeepers who are comfortable coming out of the area and playing with their feet, he insists Hart could still be his first choice.
His claims his preference for Willy Caballero at the weekend was more down to the fact the Argentinian began pre-season training earlier than Hart and is therefore more familiar with the new system.
Guardiola said: "Maybe the next game it changes, maybe not. I needed the build-up and to use the goalkeeper to play quicker to arrive the balls behind the line. Willy had this quality first of all, he trained more times. He arrived on the first day.
"That doesn't mean Joe can't do that. I know the quality of Joe, he is an amazing goalkeeper. He plays for the national team and he was so important for the two Premier League (title) wins. The personality, the character, I know about."
Hart was not the only senior player omitted with long-time team linchpin Yaya Toure, playmaker Samir Nasri and £42million defender Eliaquim Mangala left out of the matchday squad altogether.
Guardiola insists there are no problems over attitude.
He said: "I speak sometimes with the players and say the reason why. They are so professional. There weren't any training sessions when they didn't show me how good professionals they are."
The exclusion of midfielder Toure, given the 33-year-old's past importance to the club, particularly raised eyebrows but Guardiola insists he remains in the frame.
He said: "I don't have doubt about that. I know Yaya from Barcelona, how he loves to play football. I know perfectly his quality."
Source: PA
