The Newcastle United striker is unsure of whether he will return to international football but Merrick, who has known Viduka for many years, is confident he will.
"I've known Mark since he was 13. He's a wonderful person, a wonderful player. I think he'll be available for the World Cup next year, and I hope he is,” Merrick said.
"Mark Viduka has always done the right thing by the Socceroos and the national team. He's the first player to come down and chat to the players when he's in town. He's a gentleman and a wonderful player and I think he will work very hard if he gets himself fit, I think he will make himself available and be a great asset to the team," he added.