Wrighty is baffled by the club's determination to see the back of someone who has served them so well since joining from West Ham for £11million in June 2001.
He told The Sun: "Frank's doing everything a professional should do. He's scoring goals, he's never a problem and is saying the right things in his Press conferences - he's just being the ultimate pro.
"If they went back on it now [and offered him a contract] it would be quite embarrassing, but Chelsea do what they want.
"They are a law unto themselves and you just don't know.
"There are all sorts of conspiracy theories why Roman doesn't want to sign him again. There's talk about Frank not wanting to take a wage cut, but he's not worried about money. He's earned money and is not bothered by getting the same kind of wages.
"I'm sure if they offered him a deal he'd sign it because he loves the club. He still wants to do well for England and being at Chelsea is going to enhance his international career. Frank doesn't want to retire from England.
"I just find it very strange that a player who is an exemplary pro isn't wanted. They seem determined to get rid of the good people who are at the club.
"If Chelsea fans are going to be honest about the whole situation, it's embarrassing."