The Gunners were beaten 1-0 by the Championship side, but Wenger has said that the team he put out contained enough quality to win.
"We had 11 internationals on the pitch at the start of the game," he told reporters after the game.
"We made a massive mistake for the goal. We were really guilty on that goal. We were not good enough to win the game today, it is simple as that."
The draw for the quarter-finals of the competition will be made on Sunday afternoon.