Walsh has not played this season after being struck by a stomach muscle problem.
The 28-year-old made a return to action for Vale's second string in their 2-1 win over Stockport on Monday, having played for 45 minutes against Crewe's reserves, but has since been unable to train.
The right-back is out-of-contract in the summer and has voiced doubts over his ability to earn a new deal, but boss Martin Foyle has not yet written him off.
He said: "I never say never. There are a lot of games to be played before the end of the season.
"Walshy is on a par with everyone else in that he has to fight for a place in the team. My problem is I have not seen him train yet.
"He played half a game for the reserves at Crewe last week, but couldn't train for the rest of the week because he was ill."