Gnabry has been a regular in what has been his first proper season as a Bayern player. He's started 14 times in the Bundesliga and has played a key role as the club have eradicated the gap to early season pace setters Borussia Dortmund. He also played his way back into the German national team in the latter months of 2018 after the country's disastrous World Cup.
But while Bayern fans are celebrating that a player set to soon hit his best years has committed to their club, Arsenal fans are ruing the one that got away.
The Gunners snagged Gnabry as a 16-year-old in 2011, paying a reported £100,000
compensation to Stuttgart, the teenager's home town club where he'd been since the age of 11.
There was much hope for the talented starlet and within a year he was on the fringes of the first team, called up for the 2012 summer tour and making his debut not long after, a league cup tie against lower league Coventry in September 2012, aged 17 years and two months.
Gnabry played four times for the Arsenal first team that season, followed by 14 appearances the following campaign as he split his time between senior and reserve level. That included eight starts, plus sub appearances against Bayern, Barcelona, Manchester City and Manchester United.
That 2013/14 season additionally saw Gnabry nominated for the Golden Boy award - eventually won by Paul Pogba - and sign a new five-year contract with Arsenal.
Cruelly for Gnabry, serious injury struck in the spring of 2014 and kept him out of the first team for over a year. Some might accuse Arsenal of letting a supreme talent escape them and slip through the net, but his career path was irreversibly altered the moment he damaged that knee.
Gnabry didn't feature for the Arsenal first team at all in 2014/15 and his season was limited to just eight appearances in the second string. It wasn't until April 2015 that Gnabry, still aged just 19, appeared to be fully over his injury and back to something like full fitness.
However, the place that he had forged for himself at the Emirates Stadium had been swallowed up. The club had signed Alexis Sanchez and Danny Welbeck in 2014, while Alex Iwobi was fast emerging as the new hot young talent in north London.
Seeking first team football in a bid to sharpen his fitness after so long out of top level action, Gnabry made a loan move to West Bromwich Albion that quickly turned out to be a bad one. A 12-minute cameo against Chelsea in August 2015 proved to be his only Premier League appearances for the Baggies, with manager Tony Pulis issuing a withering put down of the loanee after two months of struggles in the west midlands.
"Serge has come here to play games but he just hasn't been for me, at the moment, at that level to play the games," Pulis bemoaned, as Gnabry's once bright career appeared to hit rock bottom.
The player was recalled by Arsenal midway through the loan but he was only used at Under-23 level and didn't play for the first team again. His last senior appearance for Arsenal had been in March 2014, ironically against future club Bayern, and the Gunners eventually accepted an offer.
#Serge2023 ⚡— FC Bayern English (@FCBayernEN) March 5, 2019
"We're delighted to have tied #Gnabry down to a long-term contract. Serge is one of our young guns and an important part of #FCBayern's future." @Brazzo #MiaSanMia pic.twitter.com/pEEJhhRAKE
Then manager Arsene Wenger expressed shortly before that £5m deal with Werder Bremen that Arsenal wanted to keep Gnabry, who had at least enjoyed a strong summer in 2016 after winning a silver medal with Germany at the Olympic Games and finishing as joint-top scorer.
"I want to keep Serge Gnabry and extend his contract," Wenger said two weeks before the winger was unveiled in Bremen. But the need for first team chances had seemingly been key in the player's decision, with Gnabry unambiguously declaring, "I've come to Bremen to get playing time, to develop further and to help the team," as he returned to Germany.
Gnabry enjoyed a strong season with Bremen, managing 11 goals in 27 Bundesliga games. It was form that prompted Bayern to trigger a reported €8m clause and offer a three-year contract. But rather than wait for his chance in Munich, the player was sent on loan to Hoffenheim to continue his development. There, he scored another 10 Bundesliga goals.
Now 23, Gnabry was brought into the fold at Bayern ahead of 2018/19 and is thriving.
Hindsight is a powerful thing in football, and while Arsenal fans may now curse their club over the loss of Gnabry for a such paltry fee, it is perhaps unfair to blame the Gunners for an oversight.
Had Wenger got his way, Gnabry would actually have stayed in 2016. But his eagerness for first team chances was the decisive factor and Arsenal simply couldn't reasonably offer those opportunities. Remember, this was a player who had only just turned 21, who had lost his way after a serious injury and couldn't command a place at one of the Premier League's lesser clubs.
Playing regularly at Bayern now, aged 23 going on 24 and with two strong seasons of Bundesliga performances under his belt, is a very different situation indeed.
It was not a luxury that Arsenal had, with a failed stint at West Brom their best reference.
Serge Gnabry has signed a new four-year contract at Bayern Munich. Was he the one that got away? pic.twitter.com/eqPlUAly8I— Arsenal FC News (@ArsenalFC_fl) March 5, 2019
Should the Gunners have stuck by him? They tried to.
Should they have seen his potential and promised him more chances? Perhaps it no longer seemed as bright in the circumstances. Therefore a change of scenery, returning home, might have been the only way for Gnabry to rediscover what had previously made him so special.
Arsenal will be jealous a former player is doing well elsewhere, but they did not drop the ball.