McGovern and Gaff are out of contract and have received big-money offers from rival clubs, which may squeeze them out of West Coast’s 2019 salary.
And Cornes thinks the Eagles will have a particularly tough time locking down both of them.
“Probably one leaves, history will tell you given it’s Round 13 and neither has signed,” he told SEN’s Crunch Time.
“At least one if not both will be going.”
Cornes highlighted that the Dockers are “due” to land a big-name player, and McGovern could be their guy.
“They’re saying Fremantle are leading the race for him, but I think he’d love to stay at West Coast,” he said.
“They’re due to land one, the Dockers.”