Former Arsenal defender Martin Keown believes Arsene Wenger's back four may now be defined by the weekend's omission of Per Mertesacker.
The German centre-back was dropped for Sunday's home meeting with Everton which the Gunners won 2-0 to recover from the Champions League debacle against Monaco last week.
Mertesacker was at fault for two of Monaco's goals in the 3-1 loss on Wednesday night but was absent as Gabriel Paulista made his first Premier League start by keeping a clean sheet alongside Laurent Koscielny.
Prior to the match, Keown indicated on BT Sport that perhaps Mertesacker being out of Wenger's line-up may produce a different result defensively for the north Londoners.
"I don't think you can point the finger at one player after the Monaco game. It's a big chance for Gabriel now, though," said Keown.
"I think it could be a defining moment in changing Arsenal's back four now, for sure.
"Mertesacker, with the experience he has in the game, should have been calling these young players back the other night, the two full-backs were just drifting up the pitch and not coming back.
"When he's been left isolated one-on-one he struggles due to his lack of pace too. Gabriel is keen to defend so he'll be relishing this opportunity to stamp a claim for a first-team spot."
