Mourinho made an emotional return to Stamford Bridge last summer, taking over from Rafael Benitez after the ill-fated end to his time at Real Madrid. After six-and-a-half years away from the club, owner Roman Abramovich chose to bring back the man who had enjoyed the most success during his ownership of the club in a bid to win trophies consistently.
Yet Mourinho's first season back at the club ended without a trophy. They finished third in the Premier League and were dumped out in the semi-finals of the Champions League by Atletico Madrid, leaving Mourinho with plenty of work to do in the transfer market this summer.
If speculation is to be believed, Chelsea are on the verge of signing Atletico trio Filipe Luis, Tiago and Diego Costa, whilst Barcelona midfielder Cesc Fabregas looks set for a controversial switch to West London having been such a hero for rivals for Arsenal.
But former Blues striker Cascarino believes that given Abramovich's previously trigger-happy approach to sacking managers, Mourinho shouldn't feel too secure in his job just yet, and that his signings must gel quickly after the Chelsea boss repeatedly described his side as 'the little horse' in the title race.
"If we look at the history of Chelsea, an indifferent start can cost you your job,” Cascarino told TalkSPORT. "This season was difficult. Mourinho spoke about what Chelsea lacked to be champions, and he was spot on. That will count for nothing ten games in to next season if they don’t look a real side.
"Roman Abramovich has sacked people for far less. Carlo Ancelotti left after being successful. They’ve had Luiz Felipe Scolari and Andre Villas-Boas. Roberto Di Matteo won the Champions League [and all were sacked]," added the former Republic of Ireland international.
"After 10 or 15 games, if Chelsea don’t look right, I’d be very surprised if Mourinho was still there. The owner will give him everything he wants but, after that, if you don’t succeed very quickly you can find yourself out of a job," he continued.