There was some shock but a lack of surprise when Arsene Wenger handed in his team sheet an hour before Arsenal's game against Everton was due to get underway. It wasn't that Olivier Giroud had started despite his well-documented failing against Monaco but Per Mertesacker's position on the substitute's bench.
Wenger told press before the game that the decision had been taken because Mertesacker had played a lot of games, which is true. The Germany international has started 25 of Arsenal's 27 Premier League games, eight of their nine Champions League games and one of their three FA Cup game.
That is a lot of games for a 30-year-old who has openly admitted that he is struggling for motivation after reaching the pinnacle of football by winning the World Cup in the summer. It is no surprise he was rested, but there is more significance to it than that, as former Arsenal defender Martin Keown noted.
He told BT Sport: "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.
"I think it could be a defining moment in changing Arsenal's back four now, for sure."
Arsenal's vice-captain must be exhausted both mentally and physically after a prolonged period of playing football. His World Cup exploits allowed next to no rest while Wenger's lack of defensive cover has left him with little chance to rotate.
Mertesacker showed the first real signs of this fatigue against Monaco where he seemed unable to fulfill his duties as captain, allowing Arsenal to continue with their suicidal tactics that lead to a 3-1 defeat.
He didn't stand up and take charge when the situation was deteriorating and that has not gone unnoticed by Wenger. Something was wrong with Mertesacker.
A new beginning
Luckily, Wenger saw this coming and signed one of his centre-back targets. Gabriel was brought in from Villarreal in the January transfer window and has so far sat on the bench. He started against Everton and thoroughly impressed.
There were some obvious communication issues and it is clear the Brazilian is used to having more time on the ball than any Premier League opponent would allow. But a spectacular tackle on Romelu Lukaku in the first half, coupled with six interceptions made him statistically Arsenal's second best player, according to Who Scored.
On another day his mistakes would have been punished, but the early signs are promising for this new arrival. The more he plays, the quicker he will bed into this team and it should be Mertesacker who takes the fall.
Mertesacker is the ultimate professional and has rightly earned the respect of everyone in the Arsenal dressing room, but he is now being specifically targeted by opposition hoping to take advantage of his chronic lack of pace.
Wenger does not helping by insisting on a high line, which has in turn left Arsenal vulnerable to counter-attacks this season. Manchester United and Monaco are two teams who have experienced significant success at the Emirates exploiting this flaw.
Time is up
Gabriel enjoys pace that is at least equal to that of Laurent Koscielny. His tracking back contributed significantly to help stem to counter-attacks of Everton and gave them a clean sheet that otherwise may not have been.
Mertesacker has an £80,000-a-week contract until 2017 and does not need to be sold; his position within the squad is too valuable as a role model to both young and established stars. However, his status as a first team player needs to change.
Do you think Per Mertesacker is still good enough for Arsenal? Do you think he should be on the bench or sold ASAP? Give us your views in the comments box below!