The England left-back, who missed last month's final World Cup qualifiers because of a rib injury, was again on the bench as the Blues battled to a dramatic 2-2 draw with West Brom at Stamford Bridge on Saturday, when a controversial stoppage-time penalty from Eden Hazard rescued a point.
Spaniard Cesar Azpilicueta has slotted into the left-back spot in Chelsea's last two matches while reports have also linked the Blues with Sevilla's 21-year-old talent Alberto Moreno as Cole's long-term replacement.
Yet while Mourinho was more than happy with the contribution of Azpilicueta, he fully expects the 33-year-old Cole to soon return to his best.
"I can make mistakes, I can be unfair, for sure I am and for sure I do that, but I always give a lot of thought to my decisions," said Mourinho.
"I decided for Azpilicueta to play against Schalke and he was fantastic. On Saturday he was very good again.
"Ashley is a top professional, he is a fighter. He has to work hard, to fight hard because the place (in the team) is his place.
"Of course it is not Azpilicueta's best position, and it is not a position where Ashley can think that he is in trouble now.
"No, he has to just to work and fight and the position is there waiting for him, no problem."
Mourinho feels his team will grow in confidence for the battles ahead with the manner in which they refused to take defeat against West Brom after falling behind to second-half goals from Shane Long and Stephane Sessegnon.
"When they scored second it is easy to die, especially for a team who played two days ago and had players who were tired," said Mourinho.
"I risked and gambled a lot, but the players have to accept that if they are scared of it, then I can't do it.
"Everything we did was because of a strong personality.
"We had a bad result, because drawing at home to West Brom isn't a good result, but we rescued a point."
Mourinho - who returned to take charge at Stamford Bridge for a second spell earlier this summer - may have come within touching distance of what would have been a first defeat in 66 Premier League home games, but the Portuguese coach insists he would not be concerned to see such an impressive statistic consigned to the history books.
"The opposition can think about it, but I don't," the 50-year-old Mourinho said.
"My record is good enough to lose a game and accept it that the record finishes.
"I have a record that I have accumulated with my English football, Italian football and Spanish football - and Portuguese football.
"When I lost that first game at home in Madrid I went to the opposition dressing room to say 'well done for ending my record'. Here I will do the same when that day comes."