The full back does appear to want to leave the club, as he is refusing to sign a new contract.
The 27-year-old has been involved in preseason, playing 60 minutes of a 0-0 friendly draw against Getafe.
On Walker-Peters, Martin told the Daily Echo: "What it means is he can help us on the pitch whilst he's here.
"We've kept him out of certain games but he's trained like a beast and he's such a fit boy. He's a brilliant athlete.
"There has been a lot of noise and sometimes it's not easy for players - but I think we're in the same position that we were for the whole pre-season.
"Now it's that close to the season, it makes no sense to leave him out anymore because he can help us if he's still here. I hope he is still here."
Martin added: "Whilst he's still here, a bit like James Ward-Prowse and Nathan Tella last year, he can definitely help us."