The 50-year-old will be formally unveiled as the new Chelsea manager, just under six years after his first spell came to a close with a terse club statement announcing he had left by mutual consent.
Mourinho will reportedly be handed a summer transfer kitty of over £100million - and among the names already linked are Napoli striker Edinson Cavani, Montenegro international Stevan Jovetic, and Xabi Alonso.
But it is the club's existing squad of players which may provide Mourinho with his biggest headache as he considers what to do with the likes of David Luiz, Fernando Torres and perhaps even John Terry.
Terry was the driving force in lifting the club to their first league title in over half a century during Mourinho's initial spell in charge, but at the age of 32 he may struggle to replicate such a role. The club captain has one year remaining on his existing contract and Monaco are reported to have shown interest.
Mourinho may choose to reinstall Terry as the central point around which he will shape his second Stamford Bridge revolution, or he may be happy with him as a squad member. A ruthless option would be to usher him through the exit door and establish a fresh, younger figurehead for the seasons ahead.
The likelihood is that Terry will stay though, with Mourinho talking earlier this week of how the senior men who remain from his first spell in charge would remain "very important for the club and the balance of the squad".
The future of Terry's fellow centre-back Luiz may also be in doubt as he has been linked with Barcelona and big-spending Paris St Germain.
Striker Torres will be all ears, with the £50million striker surely unwilling to sink down the pecking order should the likes of Cavani come in.
Mourinho has already dropped some hints about the way he sees the first squad of his second reign taking shape, by signalling Romelu Lukaku and Kevin De Bruyne have important futures at the club. Thibaut Courtois, the outstanding young Belgian goalkeeper, may also find himself summoned back to London after two impressive years at Atletico Madrid.