Mendy has been sidelined for City’s last four games with what has been described as a “bruised metatarsal”.
But the left-back posted images on social media late on Saturday of himself at the Anthony Joshua boxing bout at Wembley.
And, much to Guardiola’s frustration, the City manager admitted Mendy, who has played just 13 games for the club since joining from Monaco last year, arrived late for treatment and training on Sunday.
Some reports have suggested that the extrovert star was up to three hours late for the compulsory session with City’s training staff and Guardiola revealed that he has spoken to him.
“The players should be here and he knows it. I spoke with him,” Guardiola told reporters on Friday.
Guardiola tried to lessen Mendy’s transgression by claiming that traffic congestion in Manchester has been a problem for a number of his players recently.
But he was clearly left unimpressed by his star, whom he warned about his excessive social media presence earlier this season, and does not know when he will be fit and available for selection.
“He was injured six-seven months last season. Now he’s injured again. Every day he’s having treatment. I’m not a physio,” Guardiola said.
“He arrived late, that happens sometimes, in the last period, a lot have arrived late because of the traffic. Manchester is under construction, the players arrive late. They have to drop their kids at school.
“I expect him back when he’s fit. Now he’s injured, he’s not a problem with physical condition.
“He’s injured and when he’s ok he’s coming back and when he decides to play he’s going to play.”
Step by step
Another injured City star, Kevin De Bruyne, is making better progress from his knee injury and will return to some parts of the team’s training sessions next week.
“He’s making the last steps, starting training in part in the next days. Everything is going well,” Guardiola said.
Guardiola, talking ahead of City’s home Premier League game with Brighton on Saturday, refused to divulge whether promising young midfielder Phil Foden will start in the game after impressing on a rare start against Oxford in the League Cup in midweek.
But he did insist that the Foden is very much in his thoughts.
“He needs to go step by step, don’t read too much, watch too much, train hard and his career will speak for himself,” Guardiola said.
“He has to make his own career. It’s important to do it day after day, especially for the young players.
“It’s not important if he starts, a few minutes, he’s part of the group, it’s about my decisions, he’s ready to start in any competition, after that he has to compete with his team-mates and sometimes it is not possible but he’s ready.”
Foden is out of contract in 2020 although talks have opened over an extended deal.
And, while Guardiola is not directly involved in negotiations, he is optimistic they will end successfully.
“I didn’t speak about it,” he said. “But I think Phil would like to be here and the club, there is no doubt, and the manager – hopefully it will happen sooner or later but I’m not involved.”