HAVANA (AP):

Miguel Diaz-Canel has five years to get started and a lot of work to do.

The man tapped as Cuban President Raul Castro's chief lieutenant and likely successor must quietly fend off any challenges from within the Communist-run island's secretive citadel of power.

He must gain legitimacy with young, and even middle-aged, Cubans who have never known a leader not named Castro. And he must deal with an exiled diaspora and American officials who were already making clear yesterday they will not be mollified by a new, younger face.

"There's going to be a huge charisma deficit," said Ann Louise Bardach, author of "Without Fidel: A Death Foretold in Miami, Havana and Washington. You go from Fidel to Raul, who at least had some of the shine of the Castro mantle, somebody who fought in the revolution."

She said Cuba faces "massive" problems, including a large public debt, dependence on Venezuela, an ageing population, decades of brain drain and one of the world's slowest Internet connections.

Whether Diaz-Canel is the man to fix all that is very much open to debate. Will Cubans accept another leader who was hand-picked from above and whose ascension, if it happens, will not come through multiparty democratic elections?

And will those passed over for the top job fall in line? If Fidel and Raul Castro are still alive, will the 52-year-old electrical engineer and former minister of higher education be able to set his own course?