The belt was vacated last month by longtime champion Danny Garcia, who had not defended the title since early 2014 and his last two fights took place at a catch-weight above the 140-pound limit. His upcoming return on August 1, will be his welterweight debut against Paulie Malignaggi.
Matthysse returns from what is the leading candidate for 'Fight of The Year' where he won a hard twelve round decision over dangerous Ruslan Provodnikov.
Last week Matthysse stated: "I'm very happy with my position and the opportunity to fight for the world title. I have full confidence in beating Postol. He is an unbeaten, but his fights were mostly in Europe. I've seen some of his fights. He bears a resemblance to John Molina. It's sure to be an interesting fight."
"Personally I can say that I've improved jab. I used it a lot with Provodnikov. I did several different things,. I change my style quite a bit so the Russian couldn't figure what I was going to do."