The Blues boss has praised the swift manner of his club's transfer dealings in pre-season.
The Blues boss feels the club 'did a fantastic job' in the transfer market, recruiting all the players they needed by the end of July.
Consequently, Mourinho believes there is no pressure on his side in terms of transfer dealings.
"We are very calm," Mourinho told reporters.
"My club did a fantastic job, not just because they got what we need but also because the club did it in a record time.
"The market for us was almost closed by the 31st of July instead of the end of August.
"So we are very calm; for us, the Sky Sports countdown clock that you have all the time, there is no tick-tock!"
Chelsea host Leicester City on Saturday, having topped the Premier League table with their opening-day win at Burnley.
Mourinho's men went a goal down to the newly promoted side but goals from new signing Costa, Andre Schurrle and Branislav Ivanovic gave them all three points and sent them to the league summit based on goals scored.