Legendary Manchester United boss Sir Alex Ferguson has sent former FC Barcelona coach Pep Guardiola a warning ahead of his reign at Manchester City.
The Scotsman, who lifted 38 trophies during 26 years at Old Trafford, has suggested that Guardiola might find life in the Premier League more difficult than he realises.
"English football is not easy. Every foreign coach that has come to England will tell you that," Ferguson told Sky Sports.
"Arsene Wenger, after a few months, he was talking about that. Jose Mourinho, after his first season, realised what he had achieved was hard work.
"So he will be a success. I don't think he'll ever replicate what he did at Barcelona, but that's a high standard. They were the best."
The 74-year-old also insisted that City's players are going to have to give it their all under Guardiola, or risk facing the exit door.
"Pep, without question, has a fantastic work ethic about him," he added.
"He demands that from all his training sessions, so anyone who thinks they're not going to work hard, he'll say they're not going to last long.
"I'm sure of that, he has great coaching ability."
Guardiola is currently still chasing three titles with Bayern Munich, but will leave the German giants at the end of the season.
Do you think the Spaniard will be as successful at City as he was at Barcelona or Bayern? Have your say in the comments section below.