Ulster centre James Hume looks likely to miss Saturday's crucial Heineken Champions Cup meeting with La Rochelle on Saturday, but the province are hopeful Iain Henderson and John Cooney could return at Kingspan Stadium.
Hume is following the graduated return-to-play protocols following a concussion in Sunday's 39-0 defeat to Sale Sharks, and with a six-day turnaround to the visit of the defending champions, it looks unlikely he'll be line out against Ronan O'Gara's side.
Henderson and Cooney are both also following the return-to-play protocols from incidents in the defeat to Leinster, but the province say they are tracking well ahead of Round 2.
Jacob Stockdale is a doubt for the weekend, with the wing currently being assessed for a leg injury.
While Ulster have lost just three games this season, they've found themselves in something of a mini-crisis in the last couple of weeks, with their second-half collapse against Leinster at the RDS followed up by a whitewash against Sale in the Champions Cup, the first time they had been held scoreless since 2008.
"We've got to own a 39-0 defeat, don't we?" McFarland said.
"It's very difficult when you're an honest group like these guys are. We measure ourselves by certain standards. We'll look at what we think we got wrong and have a good look at how we fix that.
"I'll come back to the point, it was a 39-0 defeat. We can play a lot better than that so we have to own that. We were bitterly disappointed with our performance."
And the Ulster boss (above) says he expects his side to rise to the challenge posed by La Rochelle.
"I'd rather be playing the European champions who put 40-odd points on Northampton in one half of rugby than playing a URC game.
"The challenge for us this week, and what we've talked about, is having a reaction. What happened at the weekend is the kind of situation where that's what we want to look for: a reaction. I know I'll see that at the weekend.
"Whatever the context, whoever you're playing, makes it easier to be on the money against a team as good as them, one of the best two teams in Europe," he added.
With Interpro games against Connacht and Munster coming in the next two weeks for Ulster, Saturday's meeting with La Rochelle is important, both in the context of the Champions Cup, but also for their confidence going forward.
And while McFarland says he's expecting a reaction from his players, he doesn't want his side to lose focus from the task at hand against O'Gara's defending champions.
"Any game in the Champions Cup is massive in its own right," he said.
"It's really exciting in and of itself. You don't want to make it all about what happened last week, it is what it is.
"The approach might be slightly different if we went to Sale and won by 40 points, you would have a completely different angle to it, but it is what it is."
Watch Leinster v Gloucester in the Champions Cup live on RTÉ2 and RTÉ Player on Friday from 7.30pm, follow our live blog on rte.ie/sport and the RTÉ News app or listen to live commentary on RTÉ Radio 1 Extra
