David Haye has branded James DeGale "unproven" ahead of his May 21 clash with George Groves.
DeGale defends his British super-middleweight title against Commonwealth champ Groves in a mouth-watering match up at the O2 Arena.
And Haye believes Groves has the edge because he's had tougher fights in his pro career.
They include a clash with Kenny Anderson in which Groves climbed off the floor to win.
In comparison, DeGale has breezed through his professional career, including a win in his last fight, against Paul Smith, to win the British title.
"He's passed a gut check - James DeGale hasn't," Haye said in an interview with Sky Sports News.
"I'm not saying DeGale can't pass the gut check, but he is unproven at this stage, he hasn't had to do it yet."
Groves, who has been sparring Andre Dirrell in Miami, added: "James is good at throwing from a distance, throwing insults from the end of a table.
"But when we're face to face it's a totally different ball game. He talks at me like I'm a child - I'm not, I'm a 23-year-old man. As soon as it dawns on him, that's when he's going to be in deep water."