Before Arsenal signed Mesut Ozil five years ago, nobody believed Arsenal were crying out for a signing like Mesut Ozil.

After all, Arsenal's attacking quartet in 2012-13 was very balanced, with all four players -- Olivier Giroud, Theo Walcott, Lukas Podolski and Santi Cazorla -- reaching double figures in terms of Premier League goals. The consensus was that Arsenal required the types of player Arsenal always seem to require: a solid defensive midfielder, or a commanding centre-back. Maybe a top-class goalkeeper, maybe even a more mobile centre-forward.

But, in addition to Yaya Sanogo and Mathieu Flamini, who cost nothing, Arsenal paid for only a single player that summer: Ozil. It was an extraordinary sum of money, too: £42.5 million, which doesn't seem particularly excessive after half a decade of unprecedented transfer-fee inflation, but was three times Arsenal's previous biggest outlay.

Ozil was considered a once-in-a-generation talent, a player so wonderfully gifted that Arsenal made an exception in both financial and tactical terms, spending a massive sum of money on a player that wasn't strictly necessary. It was Arsenal's most exciting signing of the Arsene Wenger era, with Ozil expected to define the club for years to come.

Five years on, Ozil's impact at Arsenal has been mixed. Overall he's performed well, with 50 Premier League assists underlining his creative ability, and three FA Cup medals represents a respectable return, especially considering Arsenal's failure to win silverware in the years prior to his arrival. Yet Ozil remains a divisive figure. Often mocked because of his apparent lethargy, his poor body language and lack of physical presence, arguably the greater problem has been Arsenal's inability to accommodate him, and the players around him, in the right tactical system.

The peculiarity of Ozil is that, for such a highly-renowned footballer, he largely excels at only a couple of aspects of football. He's outstanding at finding space, and his ability to play an incisive pass to a centre-forward is unrivalled in the Premier League. In other respects, Ozil causes problems. He doesn't regularly score goals, his pressing ability is questionable and he rarely drops into deeper midfield positions to dominate matches. Ozil is a final-third player, a between-the-lines player, a pure assister. But he needs the right players around him.

The statistics show that Ozil combined well with Giroud -- 14 of Ozil's 50 Premier League assists were for the Frenchman. But many were from set-pieces, and in another sense Giroud and Ozil didn't work well together. They were similar players, link men who wanted to play close to a purposeful player going in behind. Ozil would receive the ball between the lines, but Giroud would come short rather than testing the opposition's offside line. Giroud would receive the ball with his back to goal, and Ozil would be waiting in a deeper position rather than breaking into the space Giroud had been created. When combined with Aaron Ramsey's midfield running, sometimes it worked excellently. But as a front two, Giroud and Ozil never quite worked.

You wonder how Ozil would work with a pure sprinter, a shoulder-of-the-last-defender man like Sergio Aguero. Arsenal's speedy options have never quite worked: Alexis Sanchez disliked playing up front, while Theo Walcott and Danny Welbeck suffered from injuries. Alexandre Lacazette has also shown a tendency to come towards Ozil rather than run in behind.

Arsenal splashed to sign Mesut Ozil, but tactically they didn't make it easy for him to succeed at the Emirates. Allsport

While Ozil has only just switched to the number 10 shirt, he's almost always played that number 10 role, which has sometimes compromised the roles of others. A frustrating 0-0 draw with Chelsea late in 2014-15 was particularly telling, with three players essentially playing in the wrong position because of the primacy afforded to Ozil. Cazorla was shifted into a deeper position, where he adapted admirably, but his best form at Arsenal had come in Ozil's role, where he was voted Arsenal's player of the season in his first year.

Cazorla wasn't compatible with Ramsey, who was shoved into a wide-right position, when his sensational form in 2013/14 had come in central midfield.

The third player shoved aside because of Ozil was actually playing for the opposition: Cesc Fabregas. Upon his departure from Barcelona in 2014, Fabregas was keen to return to the Emirates. But Arsenal were now overstocked at his position, and even Wenger wasn't going to indulge yet another creative midfielder. Fabregas ended up joining Chelsea instead, where he's recorded Ozil-esque assist figures and won two league titles.

Ozil was unfortunate that the Premier League has, in recent years, become overwhelmingly dominated by pressing. Ozil isn't renowned for his work rate, and compared to Roberto Firmino, Christian Eriksen or Kevin De Bruyne, he sometimes appears a passenger when the opposition have possession. When Arsenal were thrashed 5-1 at Anfield by a rampant Liverpool in 2014 -- on a day when the Gunners had started top of the league, very much in the title race -- it was Ozil who was most overwhelmed by the sheer aggression of the opposition press, responsible for turnovers that caused two concessions. Ozil is the only player at one of the Premier League's big clubs afforded a free role in the era of presser-playmakers.

For all the assists, it's difficult to pinpoint Ozil's starring moment for Arsenal. His performances in FA Cup finals have been useful rather than decisive, and in 2014 Arsenal actually improved against Hull once Ozil was sacrificed in extra-time.

His history of individual awards tells a couple of interesting stories. He was voted Germany's player of the year in 2011, 2012, 2013, 2015 and 2016, and by rights should have been Germany's star man in a World Cup victory. But unquestionably he wasn't, instead marooned on the periphery, sporadically contributing from the left. More pertinently, Ozil was a regular on the Ballon d'Or list between 2010 and 2013, always finishing between 11th and 16th. He hasn't figured since, reflecting that his best form came for Real Madrid rather than Arsenal, under Jose Mourinho rather than Wenger.

His five years in an Arsenal shirt have produced just one genuinely top-class campaign -- 2015-16 -- the only time he was named his Arsenal's player of the season, and the only time he was a nominee on the PFA's six-man Player of the Season shortlist. Even then his campaign dipped dramatically at the midway point: 19 is an extraordinary tally of assists, but 16 came before the turn of the year, as Arsenal stumbled and lost the league to Leicester in the spring.

Ozil remains an outstanding player, and his strengths remain more decisive than his weaknesses. Arsenal's decision to hand the German an enormous new contract earlier this year reflects his contribution to the club, and with his decision to withdraw from the Germany setup, Arsenal might benefit from his extra freshness over coming seasons. But Ozil is still trying to convince the doubters, and Arsenal are aiming for a return to the Champions League, rather than a return to being champions. Ozil has defined Arsenal over the past half-decade, but not quite in the way they had hoped upon his arrival.