Martin also confirmed Rangers have accepted an offer for defender Robin Propper from former club Twente Enschede.
The Dutchman, 31, arrived last summer but has struggled to establish himself.
“I think it’s just case of Robin deciding if that’s what he wants and agreeing personal terms and stuff,” Martin said.
“I’ve been really impressed with him as a guy but obviously we signed some centre-halves so it’s going to be difficult for him to play.
“If it happens, it’s a good move for him, if it doesn’t, it’ll be because he’s decided it’s not what’s right for him and maybe he’ll look for something else.”
Rangers have so far this summer already signed midfielders Thelo Aasgaard, Lyall Cameron and Joe Rothwell, as well as defenders Max Aarons, Nasser Djiga and Emmanuel Fernandez.
“The squad’s big,” Martin said. “We can’t have 40 players in the building.
“We’re definitely not done with the signings so it’s natural that some people will need to go.
“When some people come in, it’ll be even clearer for some people that they have to go play football elsewhere.”
