Sergio Aguero concedes his early days under Pep Guardiola at Manchester City were not easy but the striker hopes his manager has helped to put five years of knee soreness behind him.
Aguero became City's all-time record goalscorer this season and was once again a key figure as the club claimed a third Premier League title since his arrival from Atletico Madrid in 2011.
The 29-year-old finished an injury-curtailed campaign with 30 goals in all competitions and back in position as Guardiola's first-choice striker.
Things have not always run so smoothly for Aguero under the Catalan, who demanded a greater all-round contribution from the Argentina star last season and dropped him in favour of Brazil youngster Gabriel Jesus.
"Guardiola is very demanding, it wasn't easy at the beginning," he said of the City boss, who signed a two-year contract extension to keep him in charge at the Etihad Stadium until 2021 on Thursday.
"After Gabriel's arriving, Pep had some alternatives for the starting XI, but at Manchester City we have a lot of matches in different competitions to show our performance."
Aguero has had to watch those matches from the sidelines after keyhole knee surgery over the closing weeks of the season after a heavy challenge from Manchester United full-back Ashley Young aggravated an existing problem.
However, he told TyC Sports his right knee has been a long-term source of discomfort throughout some prolific exploits.
"From 2013 I have been suffering. I tried to make an effort to play in the Champions League [quarter-final defeat against Liverpool]," he said.
"Pep supported me a lot. I talked with the doctors and I said that if we didn't make surgery I could lose [the chance to play at] the World Cup.
"After five years, my knee is like knew. I've always had problems but now I feel different, I can bend it and it's a relief."
Aguero is in line to star alongside his long-time friend Lionel Messi as Argentina negotiate a tricky Group D at Russia 2018 alongside Iceland, Croatia and Nigeria.
Messi has been sporadically linked with a blockbuster move to City, while the Barcelona great joked earlier this week that it should be Aguero joining him at Camp Nou.
"I think that is not possible right now," Aguero replied. "Maybe some time ago, but, at our age, we will probably keep playing in the same teams."