Liam Moore was frustrated that the Royals were overturned at West Bromwich Albion on Saturday afternoon, after a 4-1 defeat at The Hawthorns.
Reading had led 1-0 at the break following a fantastic early strike by Leandro Bacuna, but the hosts levelled early in the second half through Dwight Gayle's back-post header.
Gayle struck again soon after, before Harvey Barnes and Kyle Bartley rounded off the win for the Championship's top-scoring club.
Moore reflected on a difficult afternoon in the West Midlands, calling the performance: "Very frustrating, especially after the first half. We always knew it was going to be a tough place to come but the end scoreline is very disappointing.
"You always expected them to come out and play better than they did in the first half, we didn't get up to the levels we did in the first half - which is disappointing.
"But for the goals that went in, we've got to be frustrated with them. Two set-pieces, one where we probably could have played out, we were wide open and the next thing you know it's in the back of the net.
"It's what you've got to expect when you're playing against quality players like this, we're obviously very frustrated and it's a disappointing day."
After a solid performance in the first half that limited the Baggies' opportunities in front of goal, Moore said the Royals were disappointed to not see the result out in the second period.
"The first half felt brilliant. Our shape was very good, the press was very good in the right areas, they had a couple of chances but we looked solid.
"When you concede early on in the second half, especially away from home, they get the crowd behind them and a bit of momentum, it's difficult.
"We hoped to see it out better than we did, unfortunately we didn't and the rest is history."