London: The former Blues midfielder, who was signed by the Portuguese manager in 2006, believes the west London club will challenge for honours following the Special One`s return.
Former Chelsea midfielder and ex-Germany international Michael Ballack has backed Jose Mourinho to reinvigorate the west London club and lead them to success once more.
The Stamford Bridge outfit won the Europa League last season under interim boss Rafa Benitez, but crashed out of the Champions League in the group stages and only finished third in the Premier League - and sixth the year before.
But Ballack is adamant Mourinho can turn Chelsea`s fortunes around, and believes the Portuguese boss can get the best out of diminutive playmakers such as Juan Mata and Oscar - just as he did with Deco while at Porto - in the quest for silverware.
"Mourinho is a smart coach and can push this Chelsea team forward to win titles once again," Ballack told Goal.
"Now Chelsea have small, amazing and more skillful players, unlike his first time when the team was made up of bigger and physical players.
"At Porto, he had small players such as Deco and he built the team around them to achieve results."
The 36-year-old former Bayern Munich and Bayer Leverkusen midfielder scored 26 goals in 167 appearances for the Blues, and won the FA Cup under Mourinho in the 2006-07 season.