The former Liverpool skipper says the Blues will not be able to repeat their "lucky" feat from last season, especially without the influence of striker Didier Drogba in attack
The Blues won their first ever Champions League crown last May, but Souness reckons that feat was the luckiest ever in the history of the competition.
"Chelsea got away with it last season and they cannot approach it the same way this time," the former Rangers, Liverpool and Newcastle manager told reporters.
"It is impossible. Nobody in the history of football has ever had that much luck.
"Chelsea fans have enjoyed the memory of lifting the cup, but they wouldn't have enjoyed the Barca and Bayern games while they were taking place."
Club owner Roman Abramovich has again spent big this summer, with the €40 million signing of Eden Hazard from Lille a major signal of intent for the Blues to build on last season's success.
However, Souness maintains that Chelsea have no chance of becoming the first team to retain the Champions League unless they play in a more positive manner - and Fernando Torres scores the goals that departed club legend Didier Drogba contributed.
He added: "Roberto Di Matteo can't plan to repeat last season. Fair play to him for playing to Chelsea's strengths, but I have concerns for Chelsea in all competitions this season because their get-out-of-jail-card, Didier Drogba, is playing his football in China.
"Even if Drogba hasn't been able to do it for 90 minutes in recent years, how often did he save them by popping up with the vital goal, like he did in the final?
"I am hoping Fernando Torres can step up to the mark but they are some boots to fill, Drogba was the best centre-forward of his type anywhere. Torres is playing with a bit more confidence now, he seems to be one of those players who needs to be loved to produce his best. But will he ever get back to his Liverpool best? I'm not sure."
Chelsea begin their defence of the biggest prize in club football when they face Italian champions Juventus at Stamford Bridge on Wednesday evening.