Keith Thurman believes that British welterweight Amir Khan needs to "make a statement" to establish himself towards the top of the 147lbs division.
Khan has recently been linked with mega fights against the likes of Floyd Mayweather Jr, Manny Pacquiao and Kell Brook, but Thurman, who currently possesses the WBA title, has insisted that Khan doesn't deserve to be regarded as one of the best in the weight class.
The 26-year-old told Sky Sports News: "Amir Khan is still over-rated because he is yet to face a a true welterweight.
"He keeps picking the right fights and the right time. Devon Alexander? They could have both fought at 140lbs a year-and-a-half ago. But fighting at 147? That is not a welterweight fight.
"He needs to fight Shawn Porter or Kell Brook. If he wants to make a statement in the welterweight division, he should fight myself. There are several ways he can make a statement."
Thurman will make the first defence of his title against Robert Guerrero in Las Vegas on Saturday night.