The Gunners proved flat at the City Ground at the weekend as they trailed 2-1 at half-time before conceding another two after the break to crash to a 4-2 loss.
Manager Wenger had used the occasion to give some of his fringe players a chance to impress but Mertesacker feels most of them failed to do so.
“The manager made a lot of changes, gave a lot of trust to players who haven’t played a lot recently and I don’t think anybody justified their selection today,” said Mertesacker.
“In the first half we played in the park a little bit. We were not precise, especially in the final third. We couldn’t create a lot of chances.
“In the second half there was a little bit more spirit from ourselves, but in the duels you could see that they out-battled us and that little momentum never really changed.
“When we scored to make it 3-2 and when he miskicked the penalty, obviously we expressed it to the ref but he didn’t listen.
“It’s difficult to take because for those players who played today, that was probably a last chance to show up and show the manager that they’re ready to play more games.
“It’s not the case anymore.”