Two seasons ago, Bayern Munich had the world's best defensive midfield in their double pivot of Bastian Schweinsteiger and Javi Martinez. They also boasted the best full-backs in Philipp Lahm and David Alaba.
Since then, coach Jupp Heynckes has been replaced by Pep Guardiola, who has changed the team again and again. Bayern now no longer play with full-backs, at least not in the full-back positions. Lahm and Alaba started for the first time as the double pivot in Sunday's 4-1 DFB-Pokal win over Preussen Munster.
Neither Martinez nor Schweinsteiger was available to play in Sunday's match, but SportBild (h/t @Lupin5) reported even before the former's cruciate ligament injury that Alaba and Lahm were Guardiola's preferred combination in front of the back three, at least in Thiago Alcantara's absence.
After a convincing performance, albeit against third-tier opposition, there is the very real possibility that they will remain Bayern's holding pair for the foreseeable future, especially with Schweinsteiger currently (per Bild) suffering from chronic patellar tendon problems that will keep him out until mid-September at the earliest, and Thiago (per The Guardian) having suffered a setback that may see his knee injury sideline him until October.
As natural full-backs, Lahm and Alaba bring different qualities to the Bayern midfield than Schweinsteiger, Martinez, Thiago and Sebastian Rode. They are less experienced in the role, the German having only played in the position a few times prior to last season and the Austrian only ever filling in centrally for his national team. Both are very smart, technical and extremely adaptable players, though, and it's foreseeable that they will become a reliable and functional unit in the weeks and months to come.
Lahm is the smaller and less athletic of the two; his diminutive size and modest pace alongside the similarly slow Schweinsteiger and Toni Kroos cost Bayern last season, especially against faster, counterattacking opponents in the Champions League. Alaba, on the other hand, has blistering pace and is lightning-quick to the ball. Although also not exactly a hulking specimen on the physical end of things, the 22-year-old brings much-needed qualities to the Bayern midfield.
In addition to Alaba's quickness, Bayern will benefit defensively from the presence of two natural defenders in midfield. Although both can join in the attack, there won't be many concerns about the pair being caught too far upfield and trying to force things in the attacking third. Both have great tactical nous and are clean tacklers. Alaba has the attributes of an exceptional ball winner: quick, decisive, great instincts and an exceptional ability at closing down space.
On the one hand, Lahm and Alaba's lack of attacking impulse is a good thing, at least for the team's tactical balance. On the other, it means two fewer threats in deep areas. One option Bayern had with Kroos was that he could always draw a defender out of position due to his lethal ability to shoot from distance with both feet. Alaba is certainly a danger with his left foot, but he will be less of a concern for defenders than the sharpshooter Kroos. Similarly, Kroos had a better eye for playmaking and finding his way into the penalty area than Lahm and Alaba, neither of whom look entirely comfortable when in and around the box. That comfort can come with experience, but it will take time to develop.
In terms of technique, Lahm and Alaba are both exceptionally gifted with the ball at their feet. With a soft first touch and the ability to play touch-and-run passing sequences, they are anything but Javier Mascherano-types. The one thing both players are missing, though, is ball-playing quality on their respective weaker feet. Lahm as a left-back was always limited when it came to overlapping runs due to his limited ability to cross with his left foot. Alaba is a decidedly left-footed player. In an area of the pitch that requires players to think both left and right, both will have to develop their game to make them more versatile on the ball.
It's a curious thing that such great full-backs are now being used as midfielders in a system that doesn't use wide defenders. But Lahm and Alaba are exceptional footballers overall; they aren't so specific that they are unable to adjust to their new-found central-midfield roles. There are some advantages and disadvantages to using them out of their trained positions. Whether Bayern will be better off will become clearer in the months to come.