Di Matteo's exit, six months after winning the FA Cup and Champions League as caretaker manager in the wake of Villas-Boas's dismissal, had many shaking their heads in disbelief but the Portuguese, now at Tottenham Hotspur, was not surprised.
"It's their decision, it's what they think will take them forward," Villas-Boas, who replaced Harry Redknapp at Tottenham in the summer, told the BBC.
"At Chelsea, I think another sacking is just like any other day at the office. That's my interpretation."
Chelsea owner Roman Abramovich has now ended the reign of eight managers since taking control of the club, although Di Matteo's has in some ways been the most shocking after taking the club to the 'Holy Grail' of Europe's top club prize.
"He has achieved so much in such a little amount of time," Villas-Boas, who worked alongside Di Matteo during his short spell in charge at Chelsea, added.
"His CV is maybe one of the best in the world now - he has won the Champions League and the FA Cup too.
"It was difficult for Robbie and I wish him well for the rest of his career."
Arsenal long-serving manager Arsene Wenger said he was left shocked by the news from West London earlier in the day.
"I find it surprising and very sad," Wenger told reporters after his side's 2-0 Champions League win over Montpellier.
"Personally I believe it's important on our side to show loyalty. Di Matteo came in in a difficult situation he has won the Champions League and the FA Cup and he has done well and was not given any time at all this season."
Spaniard Benitez, who took Liverpool to the Champions League title in 2005, has only been made "interim manager" by Abramovich - another surprise for Wenger.
"Benitez is a guy that has a record, he is a manager of stature and it's a surprise that he's been appointed for such a short time and a surprise that he accepted that."
Real Madrid manager Jose Mourinho, who won successive Premier League titles for Chelsea after being head-hunted in the early years of the Abramovich regime but left after falling out with the Russian in 2007, sympathised with Di Matteo.
"I am never happy when a manager is sacked," he told journalists after his Real side drew 1-1 with Manchester City in the Champions League. "It can happen to them, it can happen to me. I am never happy and I never enjoy it.
"I feel sorry for him and feel sorry for his family because our lives are very similar.
"Everyone knows I like my old teams. I like Chelsea, I like Inter, I like Porto, I like my old clubs to win and always wish the managers well at my former clubs so I wish well to Benitez at Chelsea now."
