He had a loan spell at Yeovil Town at the end of 2008/2009 and last summer had then had a trial at Championship side Crystal Palace last summer and picked up a knee injury with the Selhurst Park club.
Gradi told the official website "Danny's grandfather asked if we would have a look at him because he had a bit of bad luck with an injury"
"He had a cruciate injury and went out of contract after spending most of his young career at QPR.
"We said that we would have a look. I am not saying that we would be in a position to offer him anything, but he has a chance if he is good enough because I haven't got another one ready enough to go in at the moment if one of the main ones gets injured.
"He was very impressive in training and we will continue to have a look at him. He looks fairly fit and has worked hard over the summer. Our physio has looked at him and his knee is fine, so we will see."
Polish Goalkeeper Bartek Fogler is training with the Railwaymen and will start in goals for the trip to Nantwich Town on Saturday. Fogler who had a trail with Bristol City last summer then a few days later had a trial with Blue Square Premiership side Wrexham.
Fogler could be signed on a short term deal as cover for Rhys Taylor who is on loan from Chelsea.
25-year-old Fogler has been looking for a move to England to be with his girlfriend who is studying at University and last season he turned down a move to Polish Premier side Legia Warsaw.