There have been outgoings at Wrexham this summer, with striker Paul Mullin joining Wigan Athletic on a season-long loan, plus Ryan Bolton moving to Mansfield Town and Will Boyle joining Shrewsbury Town on permanent deals.
Parkinson says more players will head out of the club before the new season, which starts away to Southampton on Saturday, 8 August.
Full-back Jacob Mendy is set for a loan move.
“Everybody knows the numbers situation is there. It’s a 25-man squad, including the goalkeepers,” Parkinson said.
“I’ve just spoken to Jacob Mendy about that. We need Jacob to go and play this season for himself.
“He’s a great example of that, a bit like Jordan Davies was last year who got to the stage where he needs to play. There’s a few players in that category.
“I’m just mentioning Jacob because I’ve just been speaking to him. There’s several clubs who want to take him on loan.”
Parkinson says he will help Mendy find the “right club which suits him”.
“I’ve got a lot of faith in Jacob, but he’s just missed quite a bit of football last season for one reason or another,” he added. “He needs to get back going again.
“Ine thing we’ve always tried to do is be fair to all the players because a lot of those lads have done so well for us.”