It was the first time during the centre's international career that he had been dropped since making his debut for Ireland in 1999.
The lock told Today FM: "I was shocked and disappointed. After playing so long with him you end up being a bit of a fan. I wouldn't say it took the gloss off it a little bit for me, but it probably did.
"It's a shame he wasn't out there. Even going on the bus with him, I was injured and there were other guys resigned to the fact that they weren't on the team.
"I thought Brian was playing well. If you look at the first two Tests there wasn't a whole lot of quality ball given to the back line. So it's hard to fathom the logic behind the decision, certainly from my point of view."
The Lions won the match 41-16 to seal a series win.