Pep Guardiola and Man City to begin their ascent up the mountain after 'once in a lifetime' season

For Pep Guardiola and his Manchester City players, the comedown has started from the club's greatest ever season.

"We climbed the highest mountain with what we have done," Guardiola said on Thursday, in reference to City winning the Premier League, FA Cup and Champions League for a rare treble.

"The last two days, we came down the mountain." The new season starts in earnest on Friday when City opens the Premier League with an away match against Burnley, and it means a 10-month slog begins again.

Guardiola knows that too well and he pretty much acknowledges life will never be as good for City again.

"I don't think it will be possible to do again what we have done last season," he said.

"It's once in a lifetime. So I said to the players, Forget about it." "There will be a lot of difficulties," Guardiola added, "to climb as high as possible the mountain and we will see that our football, our behaviour, our mentality, will dictate how the season will be. What we have done remains in our hearts, our minds. How nice it was. But it's over ... it's almost impossible to repeat." City has more games on its schedule — the UEFA Super Cup against Sevilla takes place on Wednesday and there is the Club World Cup in Saudi Arabia in December — and there is a general feeling that City might need to strengthen its squad, especially in attack, to handle it.

Midfielder Ilkay Gundogan has gone to Barcelona and been replaced by Mateo Kovacic.

Defender Josko Gvardiol has come in, most likely to replace Aymeric Laporte, who appears surplus to requirements.

City has sold winger Riyad Mahrez to the Saudi Arabian league and he hasn't been replaced. Cole Palmer, a 21-year-old academy product, has been viewed as a potential replacement but Guardiola couldn't guarantee Palmer would still be at City by the end of the transfer window amid interest from West Ham.

Another winger seems necessary if City is to be as dangerous as last season, especially with potential title rivals Arsenal and Manchester United having strengthened during the offseason.

The biggest threat to City, though, is likely to come from within.

Can the players, Guardiola and his coaching staff rouse themselves again? The European Cup has finally been won and there is another big target in view — City could become the first team in English history to win the top flight in four straight seasons. Maybe that can be their motivation as the season cranks into gear.

"We have to challenge ourselves," he said.

"I cannot do it for myself. My staff have to challenge me. I have to challenge them and the players. They have challenge me. I have to challenge the players. We have to push each other. If people expect I'm the only one to do it, it will not be possible.

"I have to admit, I'm really surprised — after so many years having these doubts — that we respond amazingly. We start again. We will see." Some other things to watch out for ahead of the first round of games: LONG GAMES Get ready for some long, long matches in the Premier League this season.

In an attempt to deal with a decline in effective playing time, the league will be adding more minutes at the end of each half to make up for stoppages for goals, substitutions, celebrations, time-wasting and other things.

The Premier League is predicting games will last, on average, 3 minutes and 23 seconds longer than last season.

Sunday's Community Shield, when Arsenal beat Man City on penalties, showed the significance this can have. Arsenal scored its equaliser in the 11th minute of stoppage time to take the game to a shootout.

HAALAND DROUGHT It's six games — if the Community Shield is included — and counting since Erling Haaland last scored a goal for Man City.

Have defenses figured out a way to stop last season's top scorer in the league, with 35 goals? Or is this just a blip for a striker who took scoring goals in English soccer to new levels? Haaland slowed down at the end of last season pretty much once City had the league wrapped up, with the drought also taking in the wins in the FA Cup final against Man United and the Champions League final against Inter Milan.

It would be no surprise if he gets back up and running against promoted Burnley at Turf Moor.