Holmes is looking for a new club after being released by Huddersfield at the end of the season.
The American-born star came through the ranks at Huddersfield, but with his contract expiring in the summer the club decided not to offer him a new deal.
Holmes broke into the Huddersfield first-team in the 2013-14 season and there were high hopes for him as he made 19 appearances for the club during that campaign.
The 21-year-old failed to make the desired impact the following season, but the club still took up the option of a one-year contract extension last summer.
Holmes struggled to hold down a place in the side under David Wagner this season and he was happy to let him move on as he reshapes the squad at the John Smith's Stadium.
A number of clubs have been alerted to Holmes' availability with the likes of Charlton, Barnsley and Portsmouth registering an interest in the attacking midfielder.
Chalrton fan protests on the pitch
Charlton are hoping to win the race for Holmes' signature as they look to build a side capable of winning promotion back to the Championship next season.