Hartlepool United are sweating on the fitness of defender Keith Watson.
The centre-half was withdrawn in the dying embers of Saturday afternoon’s 2-1 win at Leyton Orient.
And Watson, on loan from St Johnstone until January, is being assessed by the club’s medical staff over the course of the next 48 hours to determine the extent of the damage.
“It is one of them things,” said Harrison about the Scot’s unfortunate problem.
“We will have to wait and see. Over the next few days we will know more.
“The medical staff will assess it and we hope it is not a bad one because he has been immense for us since he has come in.”
Watson was a key component in Harrison’s plans, in his own words, to frustrate Steve Davis’ side.
It didn’t work from the off, but the manager was pleased with the way it worked out, particularly in the second 45.
“We knew what we had to do - in the first half the gaps were too big between the lines. We changed that, became more compact,” he said.
“Things didn’t go the way we wanted.
“The game plan changed. They played differently to how we thought so we had to adapt.
“They are a good team, want to pass and we wanted to frustrate them. I think we did that in the second half.
“We made it hard for them. To go there and win here is fantastic. The players deserve it, though. They worked hard.”