Bayern Munich have swelled an all-conquering midfield with the acquisition of Germany international Leon Goretzka from Schalke.
Watch: Bayern looking to future with Goretzka signing
In many ways, Goretzka is the complete central midfielder. Tall (6'2"), rangy and with a fantastic motor, he has been compared to retired great Michael Ballack and Germany international Sami Khedira on account of his ability to bind defence with attack. He is also well-known for his gazelle-like bursts into opposition territory, scoring four Bundesliga goals in 11 appearances so far this season alone.
His weaknesses are few and far between, although he has had his fair share of issues with injuries and has only produced 10 assists in 102 Bundesliga appearances to date. Nevertheless, what he lacks in creativity, he more than makes up for in work rate and application. Moreover, the Bochum youth product has the ability to operate as a No.6, No.8 or even a No.10, ticking a crucial box next to 'versatility' in Bayern’s post-Pep Guardiola wish list.
The burning question is: who, if anyone, makes way for the midfield ace?
Martinez is one player the current Bayern setup cannot do without. Reinstated to his preferred defensive midfield role by Jupp Heynckes, the Spain international brings an unparalleled level of stability to the side. He underpinned the club's unprecedented 2012/13 treble win, and has won 14 of his 15 assignments under the returning Heynckes this term.
James has also rediscovered his best form since Heynckes stepped in to fill the void left by Carlo Ancelotti at the start of October. The Real Madrid loanee enjoyed great success in the wider attacking areas in his first three seasons in Spain, but has found a new niche at Bayern in the hole behind lone striker Robert Lewandowski - producing three goals and six assists.
Watch: 60 seconds under pressure with Leon Goretzka!
Assuming Martinez can stay fit - he missed large parts of the 2013/14 and 2014/15 campaigns through injury - and James remains a red at the very least for the duration of his two-year loan deal, that leaves four current players - Vidal, Sebastian Rudy, Corentin Tolisso and Thiago - and only one central midfield vacancy in either a 4-2-3-1 or 4-1-4-1 formation.
For now, Vidal appears to be Heynckes' preferred choice, for the most part alongside or in front of Martinez. The Chile international is not afraid to get stuck in defensively and is an expert at turning runs from deep into goals - five this term, including four in successive games between Bundesliga Matchdays 12-15. That being said, he will turn 31 at the end of the 2017/18 season and only has one more year left on his existing deal with the club.
Further down the pecking order, 23-year-old Tolisso - with two goals and two assists in 16 appearances - has performed admirably in his debut Bundesliga season and, until confirmation of Goretzka's move, looked a safe bet as Vidal's next in line in the Bayern midfield. Rudy has his merits, but has typically - and sporadically - been rotated in for Martinez, while Thiago - the matador with creative powers on a par with James - has been restricted to just four Bundesliga appearances under Heynckes due to injury.
Watch: Check out Goretzka's top five goals in the video below!
There has been talk that Heynckes might be tempted to extend his stay beyond the end of 2017/18, but even if he doesn’t, the 72-year-old will doubtless make a telling contribution to Bayern's search for a long-term successor. Good news for the incoming Goretzka, especially in light of the record champions' penchant for forward planning and Heynckes' past glories implementing a double midfield pivot.
In Joshua Kimmich, Bayern have long sourced the natural heir to retired captain Philipp Lahm at right-back. Summer 2017 signing Niklas Süle (also 22) is already a regular fixture in central defence, while Kingsley Coman (21) and Serge Gnabry (22) have the necessary credentials to one day inherit the flanks from evergreen wide men Arjen Robben and Franck Ribery.
One former player whose boots have yet to be adequately filled, however, is Bastian Schweinsteiger. The eight-time Bundesliga winner left Bayern for Manchester United in summer 2015, but will forever be remembered as one of the finest servants in the Bavarian giants' decorated history.
Aptly enough, Schweinsteiger's career highlight at club level came not just under Heynckes, but as Martinez's sidekick, in 2012/13. The duo, with their disciplined defensive engagement and positional awareness, knew how to pick their midfield battles and when to launch attacks into opposition territory. Bayern might not have swept to an historic Bundesliga, DFB Cup and UEFA Champions League treble without them.
It is memories of Heynckes' acclaimed Martinez-Schweinsteiger double pivot that make the Goretzka transfer so appealing. Ballack, Khedira, Vidal and Schweinsteiger rolled into one: the outgoing Schalke star is the midfield engine set to drive Germany's most successful outfit to even greater heights in the years ahead.