The former Barnet frontman, who scored 10 goals last season while on loan at Millwall and Charlton, returned to training at Thorp Arch last weekend.
And Grayson insists he and several other players who were on the fringes for large parts of last season, such as David Prutton, could be handed a second coming in the first-team if they impress in pre-season.
Grayson told the Yorkshire Evening Post: "He's come back here and is under contract, any player that is under contract has got an opportunity to impress, I'm not discarding anybody.
"Prutts has come also back and is looking fit and sharp, as a lot of the players are.
"Whatever they did last year is history to a certain degree. It's a new season and new start for everybody. The players will all be given their opportunity to play football and then we'll go down the line of seeing who will be staying and going."