The Blues have been heavily linked with a big money move for the Brazilian throughout the 2013/14 season, who scored from the spot in the Champions League at Stamford Bridge.
"Chelsea will be quite quiet in summer," Mourinho said.
"We are going to do some critical signings.
"A striker? Yes.
"We have some basis for the improvement of next season, and we need that.
"Some teams need years and years to be built."
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