Anthony Joshua claims he wants to see fellow heavyweight champion Deontay Wilder "fight better opposition" and really challenge himself.
The undefeated 31-year-old became the first American in nine years to be crowned a heavyweight champion in January 2015 when he beat Canadian Bermane Stiverne via a unanimous points decision at the MGM Grand to claim the WBC strap.
Wilder has successfully retained his belt on four occasions since and, having recovered from a bicep injury, he will face Gerald Washington in the early hours of Sunday morning.
Wilder has been a professional for around eight to nine years and I want to see a bit more, and there is nothing wrong with that.Anthony Joshua
Washington was drafted in as a late replacement for Andrzej Wawrzyk, who had to pull out because of a failed a drug test, and Joshua feels Wilder's choice of opponents are too safe at the moment.
Joshua, who will put his IBF title on the line and bid to add the vacant WBA 'Super' belt to his collection against former WBA, IBF, WBO and IBO heavyweight champion Wladimir Klitschko at Wembley Stadium on 29th April, told Sky Sports: "I think Wilder needs to fight better opposition.
"Washington is good, but he's up and coming still. It was a last minute call-up as well.
"I know his last opponent failed a drugs test unfortunately, but I would love for him to postpone it for another month and get someone who could train for a world championship fight."
The 27-year-old 2012 Olympic gold medal winner, who has won all 18 of his professional bouts to date and has never been taken beyond the seventh round, added: "Wilder has been a professional for around eight to nine years and I want to see a bit more, and there is nothing wrong with that.
"Good luck against Washington, but I think the other contenders in the heavyweight division need challenging as well, so I think it would be good for Wilder to force these type of fights, rather than taking easy pickings."
Joshua, who has spoken of his desire to unify the heavyweight division by facing Wilder at some point in the future, is 1/2 to defeat Klitschko in April, while the Ukrainian is 9/5 to win.
Meanwhile, Wilder is 1/1 to win this weekend, while Washington can be backed at 1/1 to pull off a surprise win.
View all Boxing betting