The Portuguese, whose remarkable record earlier in his managerial career earned him the famous nickname 'The Special One', returned to Stamford Bridge in June 2013 after three increasingly bitter years at Real Madrid.
When he did so, he spoke about wanting to establish a dynasty by bringing through a succession of winning teams. But his second stint has summed up his career in microcosm: a period of bedding in, one or two seasons of stunning success and then things fall apart.
"I had already heard it when he was in Madrid and now we have confirmation in London."
Mourinho's first season back at Chelsea saw him finish a campaign without a trophy of any description for the first time in his managerial career, but he reshaped the team brilliantly.
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In came Thibaut Courtois, recalled from a long-term loan at Atletico Madrid, Cesc Fabregas and Diego Costa, and with a galvanised spine Chelsea swept to the league title and beat Tottenham Hotspur in the League Cup final.
To watch Chelsea over the opening months of the 2015-16 season has been to watch Mourinho's whole strategy unravel at scarcely believable speed. Though overwhelming favourites to retain the title, they produced a series of bafflingly sluggish and insipid displays, losing nine of their first 16 league games and slumping to 16th place in the table.
Mourinho has always drawn strength from the battles he seeks to wage on what he perceives to be outside forces -- referees, opposition managers, television pundits -- but those battles seemed to consume him.
"Will he be loved?" former Liverpool defender Jamie Carragher asked earlier this year. "Chelsea fans undoubtedly adore him. Porto and Inter (Milan) supporters will, too. Yet beyond that? It is debatable."
Having rechristened himself "The Happy One" upon his return to England, Mourinho now cuts a forlorn figure.
Chelsea, he has admitted, is the only club he "loves" apart from Inter, where he enjoyed spectacular success between 2008 and 2010, winning the Champions League in his last season.
He is unlikely, however, to be short of offers, with his tactical acumen, attention to detail and ability to form water-tight bonds with players setting him apart as a manager of rare talent.
His brash, arrogant style may not sit easily with everyone, but after working as an assistant in the backroom staff at Barcelona and having unremarkable spells at Benfica and Uniao de Leiria, he emerged suddenly as a world-class coach at Porto in 2002.
"Mourinho was the best. For me he was. He brought my confidence to a level it had never been," said Chelsea great Frank Lampard, who blossomed under Mourinho into one of Europe's finest goal-scoring midfielders.
"It's a presence and an aura and a way with people. He galvanises people. His own self-confidence reflects back on his teams."
With eight league titles, seven domestic cups and two Champions Leagues to his name, Mourinho has few kingdoms left to conquer, but his inability to get on with key players or end Barcelona's dominance overshadowed his time at Real Madrid.