The Blues let go of Ancelotti after failing to win any silverware, replacing him with 33-year-old Andre Villas-Boas, who spearheaded Porto to four trophies last season.
The former Premier League champions paid a £13m compensation fee to bring the Portuguese manager to Stamford Bridge. However, Souness believes that the Chelsea board made a mistake.
“Chelsea are a concern for me,” Souness told talkSPORT. “The new manager and his new [backroom] team are relatively inexperienced. I worry for Chelsea.
“I just didn't see any sense in getting rid of the previous manager. I thought Ancelotti was a good manager, tried and tested at the highest level.
"The guy they have got in now is untried. Being successful in Portugal, where I worked for two years, with Porto, isn’t the biggest of deals. The way they have got it set up there, from the president down, they are more or less guaranteed success every year there."
The 58-year-old believes that Villas-Boas, who is the same age as players Frank Lampard and Didier Drogba, will struggle to unite the dressing room.
"The guy never played the game, I don't think he's been around top players all his life and he's not got that experience behind him,” he added.
“I know a lot of people will think 'so what' but you've got to be in and around an environment like that to understand what goes on.
"Nothing prepares you for management at the highest level. The reason I think Chelsea will have difficulty this year is because he's going to take a year to find out exactly what it's all about in England.
"When you look at what they had last year with Ancelotti, he has been around the block many times and won everything as a player and manager. I thought he was a perfect fit for them."
Meanwhile, reports suggest that Chelsea are prepared to up their pursuit of Tottenham star Luka Modric.