There are a lot of boxers who are not buying Floyd Mayweather Jr.'s claim that he will be retiring after his September 12, 2015 bout with Andre Berto. In fact the whole world doesn't believe it.

For how can a decorated boxer end his career on a not-so high note by facing Berto who hasn't exactly been in the boxing headlines? Though he is a former world champion, the fact remains that his career has been on the decline and such as drawn mixed reactions on why he had become the chosen one.

An obvious answer is of course that Mayweather wants to take it easy and simply go through the motions of holding his scheduled fight. But as far as the retirement angle is concerned, it is something that cannot be sold.

One fighter who doesn't buy it is Keith Thurman. Thurman is one of many boxers hoping to get the nod of Mayweather before Berto was officially announced as the undefeated American boxer's 'final' opponent. The decision of course raised a lot of eyebrows but alas the fight has been made.

For his part, Thurman is coming off a not-so impressive win over Luis Collazo last month at the Premier Boxing Champions on ESPN. Though Thurman did come out as the victor, the fact that he got hurt in fifth round and won only when Collazo was not able to continue was far from a win that was worth bragging.

Thurman has been calling out other fighters as well, Amir Khan of whom is perhaps at the top of the list. Khan says he is interested in fighting Thurman but did not reveal when that would be.

As far as Mayweather is concerned, Thurman is hoping he can get a chance to fight the undefeated 38-year-old boxer though time could be a constraint.

"I'm going to keep talking about Floyd until the day he retires. When he retires, then that means I'll no longer ever have a shot at fighting him. But as long as he keeps stepping in the ring, and as long as I want to keep competing against some of the best boxers in the world, I'm going to keep talking about Floyd Mayweather," says Thurman in an interview with boxingscene.com.

But wasn't this approach that led to Khan being shunned? Khan was ruled out for his continued criticism and calls on Mayweather so Thurman may want to re-think that strategy just in case.