The Royals gave McDermott his marching orders on Monday after seeing the Berkshire club fall to 19th on the Premier League table and Villas-Boas felt it was a poor decision, just like Southampton firing Nigel Adkins earlier this year.
"Extremely disappointing. I think it was along the same lines as what happened to Nigel at Southampton," the Portuguese told Sky Sports.
"I think sometimes you are a victim of the success that you have achieved. You do ever so well to put clubs in the Premier League and then you pay the price when probably given the best conditions to succeed.
"I think it's tremendously unfair. Obviously it's not my decision, or my responsibility, it's something that happens in the game. It happened to me before.
"I just hope that Brian is able to continue showing his qualities because it was his quality that put Reading in the Premier League."