Former Chelsea manager Avram Grant has warned Andre Villas-Boas that he must achieve immediate success to satisfy owner Roman Abramovich.
Villas-Boas, 33, was appointed by Chelsea on Wednesday, having achieved league, cup and Europa League success in his only season in charge at Porto.
"Roman is a guy who wants results and gives you everything to achieve them," Grant told BBC Radio 5live.
"He wants it as quick as you can, because he has put a lot of money in."
The 56-year-old added: "At the end of the day, football is a game of results, especially Chelsea."
Grant managed the Blues during the 2007/08 season and was sacked by Abramovich after his side came second in the Premier League and lost to Manchester United in the Champions League final.
He believes Villas-Boas's relatively young age should not count against him.
"I liked him a lot when I was director [of football] of Chelsea and he was a scout," added Grant, who was dismissed as manager by relegated West Ham towards the end of last season. "He's a nice guy, nice person and I enjoyed being with him.
"I know he's young but fellow coach Pep Guardiola was young when he started at Barcelona - and without much experience - and did a great job. Experience is important but quality and authority is more important.
"Andre did a great job at Porto. The players liked him. Players are human beings. If they [Chelsea] see he has the quality then they will support him."
Former Chelsea striker Jimmy Floyd Hasselbaink also believes that Villas-Boas should be judged solely on his abilities.
"Yes, he is only 33, but I think we should look at him just as a man on his own," commented the 39-year-old Dutchman. "He is a different manager, a different individual, so just give him a chance to succeed."