With the appointment now confirmed, Blues fans can look ahead to the new season, but the former Newcastle & Benfica boss is not as optimistic over the newcomer's prospects
The Blues announced on Wednesday that Villas-Boas had signed a three-year deal to become manager, but Souness is not convinced of his potential success in England.
Speaking shortly before Chelsea's announcement, Souness said that despite his initial success as a manager, winning the Portuguese title and the Europa League may not be as great an achievement as many believe.
“It’s not the hardest job in the world to win the league with Porto because Porto seem to have it well and truly sorted one way or another over there,” Souness told Sky Sports News.
“Having won the Europa League, he deserves a lot of credit for that, but the Europa League is not a priority if you look at our clubs who drop out of the Champions League, so it’s not a great competition to win anymore.
"Winning the Champions League and the Premier League is a whole different ball-game and he’ll quickly find that out."
With Villas-Boas being just 33 years-old, Souness says one of his key objectives early on will be to convince the players he has what it takes.
“What he’s got to do immediately is get the players on side,” Souness continued.
“At 33, some of them will be older than him and he’s a novice anyway you look at it.
“He had a great year last year but he’s a novice and I think it’s an enormous gamble given that you have got someone [Carlo Ancelotti] who had a track record second to no-one out there.
“I don’t think it [last season] was because Ancelotti made many mistakes - I would have stuck with him.
“If someone had asked me I would have said stick with the man you’ve got - you won’t get better than that."
Despite Villas-Boas' initial success in Portugal last season, Souness doubts his ability to replicate his achievments in England.
“I know it’s not the be all and end all but at 33, having never played the game, he’s come from a league that Porto generally win – it’s a big ask," Souness added.
“There’s only one competition to win out there in Europe and he’s operating in a different sphere now – it will be a whole different ball-game for him."