HITC Sport understands that Rochdale are bracing themselves for further interest in their top marksman.
The 30-year-old has one year remaining on his current deal at Spotland, and a host of clubs are showing an interest following his 22 goals in League One last season.
Henderson was second top-scorer in League One, and Dale are desperate to keep hold of him – but HITC Sport understands clubs from the Championship and League One are trying to land him.
Barnsley are the first club to make a move for the former Norwich City striker, but it is understood that the Tykes’ first offer has been shunned.
Dale are now bracing themselves for more bids, and they know they cannot expect to match some of the personal terms that will be on offer – so they could be facing an uphill battle to keep him.
Henderson joined Rochdale in January 2013 after leaving Colchester United.