Henderson has been out injured for over 18 months since September 2007 when he was forced out with a back injury. He didn't respond to treatment and the Irish international was sidelined for the rest of that season.
Henderson returned to training before Christmas but had a set back but is now clearly ready for first team football. He is on loan at Grimsby for one month in an attempt to get his career back on track.
Irvine will be glad of one player coming off the treatment table but it was bad news earlier in the week as Sedgewick was ruled out for a month with a hernia problem requiring an operation.