Barnet will check on striker Ben May ahead of the relegation six-pointer.
May, who is on loan from Stevenage, missed Monday's 2-1 defeat by Crawley with a hamstring strain.
Steve Kabba is still sidelined with a knee injury so Ricky Holmes is set to continue alongside top scorer Izale McLeod in attack if May is ruled out again.
Defender Danny Senda remains a long-term absentee with a knee problem but boss Lawrie Sanchez has no other major problems and could name an unchanged line-up following an encouraging display against promotion-chasing Town.
Barnet will drop into the relegation zone with a defeat and could also find themselves rock-bottom by Saturday evening if Macclesfield beat Crewe.
Rob Purdie may return for Hereford's make-or-break clash but full-backs Ryan Green and Benoit Dalibard are doubtful.
The versatile Purdie, who has been sidelined for almost a month, faces a race against time as he looks to recover from his hamstring strain.
However, right-back Green continues to struggle with the knock which ruled him out over Easter while left-back Dalibard has suffered a setback in his recovery from a hamstring problem. Both will be assessed ahead of the trip to Underhill.
Midfielders James McQuilkin and Simon Clist (ankle) as well as defender Joe Heath (groin) continue to miss out.
The bottom-of-the-table Bulls are currently three points adrift of Barnet, who occupy the final position of safety, with those above the Bees looking out of United's reach.
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