Not only did that dent both pride and confidence, the result also meant Leinster lost ground on Pat Lam's men at the top of the GUINNESS PRO12 table.
Time to lick their wounds is in short supply, with Leinster to take on Munster at the Aviva Stadium on Saturday.
But while McFadden is glad a chance to put things right comes so soon, he is unwilling to entertain the prospect of the same outcome.
"We're definitely hurting as a group," he told the Irish Times.
"Losing any interpro, at any stage of the season, is tough and, in the circumstances, it was even harder.
"It puts the pressure back on us in the fight towards the end of the season to stay in the top four.
"Confidence comes from a win. We'd love to be in that position from last week, but unfortunately we're not. Munster will have their tails up. We'll be wary of that."
Leinster could be boosted this weekend by the return of Jonathan Sexton, following international duty.
Sexton has not played in the GUINNESS PRO12 since January 8, but McFadden says his return would be a timely boost.
"He gave the [Ireland] guys a nice bit of direction, sometimes that's all a team needs," added the 29-year-old.
"If you've got the likes of Johnny guiding you, it makes it a lot easier. I was delighted to see him come back to form after getting a bit of flak at the start of the season.
"Hopefully he can bring that Irish form when he's wearing a Leinster jersey now."
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