Jose Mourinho has replaced Claudio Ranieri as Chelsea's new coach.
Over the last two years, Mourinho has led Porto to unparalleled success, guiding the club to five trophies.
In 2003 the club won the Portuguese league title and cup as well as earning a Uefa Cup final triumph over Celtic.
This season Mourinho has been equally successful - Porto retained their league title and also won their first European Cup final since 1987.
But what will Mourinho bring to Chelsea and how much will he change the team he inherits from Ranieri?
BBC Sport looks at what Chelsea can expect from their new 41-year-old Portuguese coach.
NO MORE TINKERING
Ranieri's chief fault was his desire to meddle with his team selections and formations - so much so that he self-deprecatingly nicknamed himself The Tinkerman.
His distinctive style of coaching was seen at its worst as Chelsea imploded after Ranieri introduced Juan Sebastian Veron and Robert Huth during the first leg of the Champions League semi-final against Monaco in the Principality.
1992-97: Worked under Bobby Robson at Sporting Lisbon, Porto and Barcelona
1997-2000: Stayed on at Barcelona under Dutchman Louis van Gaal
2000-1: Lasted only nine games as Benfica coach before resigning after a contract row and then moved to Uniao Leiria, who he guided to the Uefa Cup
Jan 2002: Joined Porto and led them to third from their lowest position
2002-3: Won league, cup and Uefa Cup treble with Porto
2003-4: Having already won the Portuguese league, Porto won Champions League final, beating Monaco 3-0
Chelsea went on to lose the game 3-1, a deficit they were never able to recover from.
But the poker-faced Mourinho, is very much a less-is-more type of coach.
At Porto, Mourinho has occasionally juggled his midfield and attack but very rarely his defence.
If fit, the back four of Paulo Ferreira, Ricardo Carvalho, Jorge Costa and Nuno Valente would be the the first names on the Porto teamsheet.
Uefa technical director Andy Roxburgh told BBC Sport: "Mourinho did his first two coaching courses with me in Scotland.
"He is very well-organised and likes structure within his teams, allied to individual talent. Talent wins you the game but only within order.
"He is very competitive and pays a lot of attention to the small details. Porto were very much a reflection of himself. He likes creative players and his team to play with high-intensity pressure."
Ranieri also lost his job because of the style of football Chelsea played under him.
Ferreira has been in superb form for Porto this season
True, Chelsea beat Newcastle 5-0 at home and Lazio 4-0 away but those types of buccaneering performances were interspersed with a fair share of drab displays.
Having been given over £100m to spend on players only for Arsenal to then canter to the Premiership title, that combination of factors proved unacceptable to the Chelsea board.
However, Mourinho is no Arsene Wenger, for whom style is almost as important as results.
Mourinho's side might have won the Champions League but their European success was hardly easy on the eye.
Style was substituted for a more pragmatic, even ruthless, approach.
Their success has been built on a miserly defence, a midfield for whom the outstanding player was the holding player Costinha and a posse of strikers - Benni McCarthy, Derlei Silva and Carlos Alberto - who loved to counter-attack.
Costinha is as sharp off the pitch as he is on it
Mourinho is fluent in five languages and Roxburgh is in no doubt about the Portuguese coach's ability to get his message across - be that with the players or the media.
"He can communicate very well with everybody and that is an important skill for a modern-day manager," said Roxburgh. "Above all, he can speak to the players in their own language."
Just as importantly, Mourinho has shown he knows how to deal with the media as well as his fellow coaches.
He taunted Sir Alex Ferguson after the pair clashed following Manchester United's Champions League defeat in Portugal.
Ferguson was unhappy over Porto goalkeeper Vitor Baia's part in Roy Keane's late dismissal in the 2-1 loss.
But pouring scorn on Ferguson's reaction, Mourinho said: "I understand why he is a bit emotional. You would be sad if your team gets as clearly dominated by opponents who have been built on 10% of the budget."
And unlike Ranieri, who was always keen to downplay his achievements, Mourinho knows his own worth.
So much so that a Portuguese psychiatrist has mooted that Mourinho is convinced he has been given a special gift of leadership from God.
With such confidence, though, Mourinho is unlikely to let Chelsea ride roughshod over him in the way they did with Ranieri.
Drogba joined Marseille from Guingamp for £4m
BBC Sport understands Mourinho has already given Chelsea owner Roman Abramovich a list of eight players he wants to bring to Stamford Bridge.
His emphasis on the importance of defence is revealed by his reported desire to sign Ferreira and Costinha.
But topping Mourinho's transfer target list is Marseille striker Didier Drogba.
The Ivory Coast international scored 19 league goals in the 2003-04 season but it was his performances in the Uefa Cup, where Marseille reached the final, that thrust him into the spotlight.
Marseille have already rejected a £17m bid from Chelsea but, with money no object to Abramovich, an offer of £23m could yet bring Drogba to Chelsea.