Exeter boss Rob Baxter will wait to see the extent of Chrysander Botha's broken leg and dislocated ankle before seeing if he needs to sign another full-back.
Botha was hurt in Namibia's 17-13 loss to Canada on Friday, with Exeter having only brought in cover for him, last week.
"We'll get him fully assessed and then we'll make a call," Baxter said.
"With a broken leg and dislocated ankle, even if it's not complicated, it could be a while," he told BBC Devon.
"If it's complicated and someone turns round and writes the season off for us then that's slightly different, we may have to have a look at things.
"We'll see how he is and we'll make our decision based on that."
Former Glasgow back McGuigan made his debut in the 18-6 LV= Cup win over Bath on Saturday, having joined the club from New Zealand side Bay of Plenty last Sunday.
And Baxter said he was pleased by the way the Namibian-born Scotland 'A' international slotted into what was an almost full-strength Exeter side.
"For a guy that turned up pretty much on Monday and started training, I think he's done pretty well.
"To get three days training under your belt and drop into quite a pressurised game at full-back when there's a lot of ball coming your way, when you look at what he did, I think he should be very pleased with that.
"If that's his start point for him and he's going to jump on from it, I'm going to be very pleased."