The Royals, who had Pavel Pogrebnyak sent off in the second half, failed to register a shot on target as they slipped back into the Premier League's bottom three courtesy of the home loss.
McDermott told reporters: "We've had a bad day at the office. For the first 43 minutes there was nothing in it.
"They scored but leading up to their first goal there was a handball. The second goal was down to us - it was a poor goal from our point of view."
Reading return to action against Everton at Goodison Park next Saturday.