The 21-year old was initially on standby for Wales but was added to the squad on Monday, ruling him out of Town's match against Oldham Athletic in the Johnstone's Paint Trophy.
Turner is concerned that time away from the club will be detrimental for Bradshaw, especially if he does not play.
"He was only on stand-by and was called into the squad very late so we assume that he is not going to be in the starting lineup," Turner told the Shropshire Star.
"It could be that he has been away for quite a number of days with very little training and very little match practice or game time. It might be detrimental to him to have been away and only sat on the bench plus all the travel, so I would have preferred him to stay here.
"He is naturally a fit lad and he has got tremendous enthusiasm for the game so the concern is just his [potential] lack of activity over eight or nine days."
Wales Under-21 face their San Marino counterparts on Friday evening.