Mertesacker and Koscielny kept 16 clean sheets for the Gunners but were also involved in heavy defeats against Chelsea, Manchester City and Liverpool.
And it is in those fixtures against the top sides that Carragher has challenged Arsenal's defensive duo to raise their game.
.@benkeablefaw we did last season on MNF before the game at Villa Park. But heavy losses in big games shows still need to be better.— Jamie Carragher (@Carra23) August 14, 2014
While Arsenal did indeed keep a huge number of clean sheets in the league last season, Opta stats show that the side conceded a lot more goals than their close rivals, especially when Mertesacker was on-field.
|Team||Pos||Clean Sheet||Goals Conceded||Apps||Mins|
Suggestions have been made, however, that any defensive struggles for Arsene Wenger's side also stem from a lack of defensive midfielders as opposed to faults within their back four.
Carragher has heeded this counterargument, though, suggesting the Gunners do need to sign another holding midfielder this summer.
The north London side have, at different times, been linked with the likes of Sami Khedira and Lars Bender, although Arsene Wenger has recently distanced himself from moves for either player.