“So from another brother to another brother – stay encouraged, Anthony Joshua. Keep your head up, Anthony Joshua.
“Stay prayed up, bro, because you’ve still got life.”
Wilder, who fights Briton Derek Chisora on 4 April in London, said the crash brought up “old feelings” from the death of his cousin, who was killed in a car accident.
“It’s tough to find the words to tell a person, but know that you are in our prayers,” Wilder said.
“My words may not mean anything in this moment in time. Maybe later on.
“I don’t know where he is mentally, emotionally, physically or spiritually, but I know that I will advise him to stay strong.”
Despite being long-time rivals, former heavyweight world champions Joshua and Wilder never shared the ring.
A proposed undisputed title fight collapsed in 2018 when Wilder held the WBC belt and Joshua was the WBA, WBO and IBF champion.
At a news conference on Wednesday Wilder discussed mental health struggles caused by issues in his personal life and said the “fire” is still in him as both he and Chisora prepare for their 50th professional fight.
“After two therapists and sports psychologists, here I am reinventing myself, reuniting myself. I know I’m back,” Wilder said.
