Considering how much of a difference Mikel Arteta has made to the trajectory of Arsenal, it’s currently difficult to revise any negativity surrounding the Emirates over the years.

Since the Spaniard’s arrival as manager of the club in December 2019 following the dismissal of Unai Emery, he has gradually transformed the sense of togetherness on and off the pitch in north London, subsequently improving results.

The Gunners took Manchester City to the wire last season, finishing second after spending the majority of the Premier League season leading the pack. While it wasn’t meant to be for Arsenal to be crowned champions, they were restored to the Champions League.

As many associated with the club know too well, it hasn’t always been rosy at the Emirates for both Arteta and those before him, as the club were away from Europe's premier competition for seven years before their return this week.

It wasn’t long ago that players would leave Arsenal for bigger things and even more recently that the squad lacked cohesion, however Arteta has induced a change in demographic, with young stars locking down their futures in north London.

Along with extending the contracts of their top talents, the Spaniard and Edu had an impressive summer of business, welcoming Declan Rice, Jurrien Timber, Kai Havertz and David Raya to the fold to bolster the side.

Gone are the days that the transfer windows were fuelled by anxiety of losing key players, although in hindsight, the Gunners allowed one player to leave far too soon in a talent that could have thrived under Arteta.

When did Serge Gnabry play for Arsenal?

In 2011, German youngster Serge Gnabry joined Arsenal’s academy from Stuttgart and spent five years associated with the north Londoners before ending his time in England to return to his homeland in 2016.

While he spent most of his time developing in the academy, the winger managed to secure 18 appearances for Arsene Wenger’s first team with his most notable performance coming against Tottenham in the FA Cup.

At 18 years old, Gnabry was influential against Spurs on a monumental occasion at the Emirates in 2014, seeing him lauded as “bright” and a player with a “good football brain” by Wenger in reaction to his display on the night.

The formidable French manager gushed over the teen, stating that he is a “strong believer” in his talents, as things looked as though they could blossom into something special for the youngster in north London.

The following year, things took a horrible turn for the winger, as he was left dejected after a loan spell at West Bromwich Albion, where he was handed just one Premier League appearance by Tony Pulis.

Speaking of his time in the Midlands, Pulis claimed that Gnabry was “nowhere near it” with reference to his ability to be good enough to represent the Baggies.

Eight years later and the 43-cap German international has won the Champions League and five Bundesliga titles with Bayern Munich, where he has been deemed good enough to play, with talent scout Jacek Kulig once backing him to become a "future legend".

Why did Arsenal sell Serge Gnabry?

Looking at what Gnabry has achieved since his dreary spell at West Brom, it becomes more and more confusing as to why he was permitted to leave north London by Wenger.

In the summer of 2016, the winger was sold to Werder Bremen for a figure reported to be in the region of £5m, a move that allowed the youngster to gain consistent game time and show his worth in his homeland.

At the time, Gnabry was not considered to be on the cusp of senior football, certainly after his disastrous spell at West Brom that left him far from being ready to jump into the first team of the Premier League side.

A player of Arsenal’s academy and a forward that showed glimpses of his true potential, the German left the club on good terms to seek a new chapter in Bremen.

What is Serge Gnabry’s market value now?

Based on what the 18-year-old showcased against Spurs on that special night in his budding career, it should have been anticipated just how good the explosive talent would become, which he quickly demonstrated in the Bundesliga.

In the 2016/17 campaign, Gnabry contributed to 13 goals in the German top-flight for Bremen, scoring 11 and assisting two to announce himself as a player to watch.

After one season, the former Arsenal prodigy was snatched up by TSG Hoffenheim, where he took his form to the next stage in the 2017/18 campaign, scoring 10 goals and assisting seven in the league, which paved the way for him to be on the move again.

The summer of 2018 marked a pivotal moment in his career, as he signed for Bayern Munich for just €8m (£6.9m), where he has since become an integral member of the side having secured 159 Bundesliga appearances so far.

Revising his market value today tells a very different story to the figure he was sold by Arsenal for and the figure he was signed by Munich at, with CIES Football Observatory valuing him at €50m (£43m).

Why is he worth that much?

Along with cementing himself as a star in Bavaria, the 28-year-old has contributed to 94 goals – scoring 60 and assisting 34 in the league – which only tells half of the story of his success.

In the 2019/20 campaign, the German won the biggest domestic prize, claiming a Champions League winners medal in a tournament that he scored nine times in to assist in firing his side to the trophy.

Since leaving north London, the winger has returned to the capital on two notable occasions in the Champions League, showing his love for Arsenal by scoring a formidable four goals against Spurs in the group stages of that 2019/20 edition.

Gnabry tormented the Lilywhites after the showdown by tweeting “North London is RED”, however his time terrorising Premier League sides was far from over, as he advanced into the Round of 16 that term and scored two goals against Chelsea.

This year, normal service seems to be resumed in terms of his form against English sides, as he scored this week against Manchester United at the Allianz Arena.

It will be hoped that Arsenal don’t meet Bayern in the tournament this season, not just for their abysmal record against the German champions, but to avoid facing the same fate as the Premier League sides before them when up against Gnabry.

Wenger will look back in shock at the price he sold the winger for, with hindsight being a wonderful thing, particularly when it comes to business in football.