Speculation regarding the Spain international's future has intensified after he was left out of the Blues' starting XI for the 0-0 Premier League draw at Manchester United on Monday night.
Reports that Chelsea are now in 'advanced talks' with Porto winger Christian Atsu are also likely to fan the transfer flames further.
Chelsea are already well-stocked for creative talent, so the arrival of another forward-thinking player would suggest that sales are imminent.
Manchester United have been strongly linked with Mata, while Arsenal boss Arsene Wenger admitted a liking for the World Cup winner on Tuesday and Tottenham have also been linked.
Mourinho, though, intends to leave his Premier League rivals empty-handed, with Mata still very much part of his plans.
The Portuguese tactician claims too much is being made of the 25-year-old's absence against United, with his withdrawal from the first team purely down to a lack of pre-season minutes.
Mourinho said in The Sun: "There is no chance Juan goes.
"He had a very small pre-season after the Confederations Cup. And during that pre-season he was injured.
"He started training two days before we played the first league match.
"He played against Aston Villa and I decided to put him on the bench against United."