Mertesacker, Walcott fail as Arsenal show no fight for Wenger in FA Cup
The debate after Arsenal's 4-2 loss at Nottingham Forest in the FA Cup on Sunday has largely focused on Arsene Wenger's team selection and whether the Gunners took their defence of the title seriously enough.
But the poor performance also laid bare some uncomfortable truths about this team that could have consequences for the rest of their season.
Here are five key takeaways from Wenger's first third-round exit in the competition:
Mertesacker can't play in a back four
Last season's FA Cup final win over Chelsea was perhaps Per Mertesacker's finest moment in an Arsenal shirt. But his final game in the competition was a reminder that age has slowed the lumbering German even more, and that he can't function in a back four these days. Wenger's switch to a back three was part of the reason Mertesacker was so good against Chelsea at Wembley -- the extra man at the back helps make up for his lack of pace and he can use his excellent reading of the game to control proceedings at the back. This was his first game in a back four since then, and Mertesacker was run ragged by speedy forward Ben Brereton.
Wenger, of course, should be well aware of the Mertesacker's limitations -- which makes his choice of formation a fairly obvious mistake. Especially since he could have used a back three of Mertesacker, Rob Holding and Mathieu Debuchy without changing his XI. Even Arsenal's Twitter account assumed that's what he was doing when the team sheets were announced, and were as surprised as the rest of us that Wenger would put Mertesacker in that kind of situation. Chances are it won't happen again.
Walcott's last Arsenal start?
If that was Theo Walcott's last start for Arsenal, it was a sad way of wrapping up his 12-year career at the club. But the loss leaves him with even fewer reasons for staying past this January transfer window. The lack of FA Cup games means he'll see even less playing time from now on, especially if this defeat makes Wenger take the Carabao Cup semifinals more seriously. Walcott has yet to start a single Premier League game this season, and will have to look elsewhere if he wants to resurrect his career. There's still the Europa League, but Wenger will have to start taking those games more seriously now as well and is unlikely to rotate as much in later knockout rounds.
The same scenario applies for Debuchy and Olivier Giroud, whose agents have been given added reason to work the phones this month.
Iwobi's development standing still
It's been two years since Alex Iwobi established himself as a first-team regular, helped by a breakout game against Burnley in the third round of the 2015-16 FA Cup. But in his 76th appearance for the Gunners, it was more evident than ever that his development has stood largely still since then.
Iwobi burst on to the scene with a blend of size, speed, skill and vision that hinted at a potential to become a unique type of attacking midfielder. Now he's in danger of becoming the latest promising Arsenal talent who remains a promising talent for his entire career. This season, Iwobi has just one goal and two assists despite making 12 starts in all competitions (and taking 24 shots in the Premier League alone). He badly needs to add more of an end product to his game -- which could still make him a formidable player -- but is starting to run out of time do so.
Yes, he's only 21, but Arsenal already have a number of other talented youngsters coming up. On Sunday it was Reiss Nelson and Joe Willock making their first FA Cup starts, and one can only hope their development will be more impressive in the next two years.
Nelson still waiting for big breakthrough
For Nelson, this was his sixth start of the campaign overall and first since turning 18 last month. Though the highly rated youngster was one of Arsenal's better players, he is still looking for his big breakthrough. Few players have come out of Arsenal's academy with the level of hype that has surrounded Nelson in recent months, and Wenger has shown his confidence in the teenager by starting him in both the Europa League, Carabao Cup and FA Cup. But he has yet to produce a goal or even an assist in those games -- something that is necessary to truly announce his arrival on the big stage.
Having previously been used in the unusual role of wing-back, Nelson finally played in a position more naturally suited to him against Forest when he was placed on the left wing. And he was one of the team's few bright spots going forward, always looking to take on a defender or make something happen with the ball. But like Iwobi, he needs to add goals to really take his game to the next level. The FA Cup could have been his great coming out party, but now his breakthrough might have to wait until next season.
Arsenal show lack of fight -- again
If Troy Deeney was watching Arsenal's meek surrender on Sunday, he was probably muttering something along the lines of "I told you so."
The Gunners have done their best to dispute Deeney's taunts since their loss at Watford, but their lack of fight was evident again against a team that just badly wanted it more.
Even Wenger's own assessment was damning on that front.
"Overall they were sharper than us, more incisive and more dominant in the challenges. We lost too many challenges to win a game like that," Wenger said.
It shouldn't have come as a surprise to Arsenal that a Championship side would be totally up for a game like this, and that they would be 100 percent committed in every challenge for 90 minutes. Sadly, it doesn't come as a surprise that Arsenal weren't up for it at all. We've seen too many examples over the past couple of seasons of the Gunners being bullied by opponents who have less skill but a lot more desire.
Though the individual players certainly deserve blame for that, the ultimate responsibility for failing to stamp out such repeated letdowns must rest with Wenger.
Mattias is ESPN FC's Arsenal correspondent. Follow him on Twitter: @MattiasKaren.