A winner from Callum Wilson in the 86th minute was enough to hand Bournemouth a 2-1 win over the Premier League side in the fourth round, and Irvine admitted it was a frustrating performance to watch from the touchline.
"I made the players aware of the quality of Bournemouth and how difficult it would be to come here, so there were no surprises," the Baggies boss told BBC Sport. "We needed to be better than we were. We conceded two poor goals.
"Whilst we were always in the game, we didn't use the ball as well as we could have used it. We just needed to be better."
West Brom return to action against Leicester City in the league on Saturday afternoon.