My guess is it's one or two things.
1. It's work related stress (McRae was absent from his position with only a few months of his contract left)
2. There is some truth in the rumours about a coaching job with Sale Sharks, Harris has walked and the Doc's has told him to take a few days off to reconsider.
How often does it become public knowledge that a sports coach/manager is off ill unless it's something very serious? I just find it odd that Harris made a post match comment after Hull KR saying it's a 'do or die' game on Sunday and he won't be there. Considering this it's not a bout of hey fever, a stomach bug or a head cold is it?