Villas-Boas revealed he considered taking Parker back to Stamford Bridge when Chelsea manager last season, before opting for Spaniard Oriol Romeu instead.
"Scott's been doing extremely well since he's come back. He's now at full fitness and a player we trust a lot," Villas-Boas said.
"Last season I thought about him. In the end I opted for Oriol but I spoke to Scott as well about coming to Chelsea. I had to make a choice between them.
"Scott's a great professional and someone of great ability. He can always give you the edge with his leadership qualities.
"He's still at the peak of the game and his age is fine. He treats himself well and is a good professional."