But the Ulstermen don't have to wait long to put things right as Exeter - who also suffered defeat last weekend, going down 35-8 at home to Clermont Auvergne - arrive at the Kingspan Stadium.
And 24-year-old O'Connor is urging Ulster to turn their fortunes around at the first time of asking.
"(Exeter) like their maul, they bring tempo to their play and you just have to stop that and stem it at source," the lock said.
"They have a couple of good backs, they like keeping width to their play, so we have to deal with that as well.
"We have our systems in play to deal with what they are going to be throwing at us. We just have to do our jobs the best we can and hopefully that will stem it. We take pride in our defence.
"Hopefully we can get off the line and get the spacing right because they play with width; we just have to man up and hit them back behind the gainline.
"You have to bring that passion and pride yourself. No one likes losing and to lose in the manner we did [in Bordeaux] is disappointing. You just have to man up and face up to the challenge that is coming next and just go from there."
Guinness PRO12 Ulster News
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