"The killer instinct is still there," Mourinho, in an interview with Sky Sports, said of the 36-year-old Ivorian who signed a 12-month contract last month after spells in China and at Turkish club Galatasaray since leaving Stamford Bridge following the Champion League final victory in 2012.
Drogba will give Mourinho a tried and tested formula in attack, where he will be vying for a place with Spanish duo Fernando Torres and new signing Diego Costa.
Didier Drogba has rejoined Chelsea
"He still has the technique to score goals and the physical strength and presence is still the same," Mourinho, who signed Drogba from Marseilles in 2004, said.
"Mentally he is the same. Every training exercise, his desire to compete and to win is always there.
"He will be an important player for us."
Almost unstoppable at times with his pace, power and strength, Drogba wrote his name into Chelsea folklore during his first spell at the club, scoring 157 goals and helping the club to the Premier League title in 2005, 2006 and 2010.
He also lifted the FA Cup four times and the League Cup twice.
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