Gonzalo Castro, Shinji Kagawa Under Threat as Dortmund Stars Return to Action

Even though Borussia Dortmund have already played three competitive matches in the 2016/17 campaign, one can argue the season is only going to start with a Bundesliga encounter with RB Leipzig at the weekend.

The oddly placed international break after the opening matchday in the German top flight made the DFL-Supercup against Bayern Munich, the DFB-Pokal first-round encounter with Regionalliga side Eintracht Trier and the Matchday 1 tilt with Mainz 05 feel like part of the preparation before the true start of what fans hope will be a long and eventful season for the Black and Yellows.

Head coach Thomas Tuchel would likely have preferred having more of his players at his disposal for training in Dortmund instead of scattering to the four winds, but he could still reap the benefits of so many of them joining their national teams.

The 43-year-old, after all, had to manoeuvre a difficult summer. Integrating no fewer than eight new faces into a squad is hard enough, but doing so while large parts of the team only return to the club bit by bit following international duty at Euro 2016 or Copa America Centenario complicated things even further.

It's no coincidence that a whopping nine outfielders started all three games. They'd all been in training for an extended amount of time and had already found their feet.

Of the latest arrivals following the tournament in France, only club-record signing Andre Schurrle has already started games—a testament both to his fitness and the fact that he played a minor role for Germany, being on the field for a grand total of 71 minutes in three substitute appearances during the group stage.

The other four players who only arrived at the start of August have yet to take a hold of their positions in the Ruhr side. Lukasz Piszczek, Julian Weigl and Mario Gotze are near-locks to become regular starters soon enough, while Euros champion Raphael Guerreiro should at least be among the first alternatives from the bench in his first year at the club.

In that regard, the international break worked in Tuchel's favour. Piszczek played 90 minutes in the FIFA World Cup qualifiers against Kazakhstan on Sunday, while Gotze started both matches for Germany against Finland and Norway, totalling about 160 minutes on the field.

The 24-year-old's inclusion in the squad had come as a bit of a surprise after Tuchel didn't deem him fit enough to make the matchday squad for the Mainz game, but Dortmund's No. 10 looked positive on international duty, setting up both goals in the 2-0 friendly-match win over Finland.

Weigl came off the bench in both matches and played only 28 minutes combined, but coupled with training at high intensity for Germany, that should suffice for the 20-year-old to make his full seasonal debut on Saturday evening in Leipzig.

With the three expected members of Tuchel's first-choice XI pushing for a place from the first whistle upon their return to Dortmund, others naturally stand to lose their position.

The situation is clearest at right-back, where Piszczek is the obvious starter, with 18-year-old Felix Passlack as a talented understudy. 

The Poland international, who told Jurgen Koers of local paper Ruhr Nachrichten (in German) that the future belongs to Passlack, will start most games and get rest whenever he needs it. Even though Passlack hasn't given Tuchel any reason to take him out of the lineup, getting Piszczek up to speed ahead of the start of the UEFA Champions League is vital.

It's not quite as simple in midfield, however.

As this writer detailed in an earlier piece, it's no stretch to call Weigl the team's most important player following the departures of Mats Hummels, Ilkay Gundogan and Henrikh Mkhitaryan over the summer. His importance was evident against Mainz, where the team struggled to advance the ball into the final third from defensive zones.

Summer signing Sebastian Rode and Gonzalo Castro formed a double pivot but had little influence on the build-up, with the duo's pass travelling "about 2.5 yards on average away from goal," as Dustin Ward noted for StatsBomb.com.

The Ruhr side desperately lacked a link between defence and midfield, and Weigl, who came on after 58 minutes, immediately improved the team's structure.

The Germany international replaced Castro against Mainz, took up his natural position at the base of midfield and allowed Rode to move into his preferred role as a dynamic box-to-box runner. Dortmund didn't create too many chances, but the team looked more decisive and organised going forward, a credit to Weigl's qualities as a balancing element.

With Rode bringing a physicality and energy to the team that the sometimes-phlegmatic Castro lacks, it seems likely that the 29-year-old long-time Bayer Leverkusen man will lose his place to Weigl.

The same fate could loom for Shinji Kagawa one position further up the pitch. On paper, the Japanese playmaker is a perfect fit for Tuchel's playing style that places high value on position play and ball-retention.

His ingenuity, technical qualities in tight areas and diligence in counter-pressing should make the 27-year-old the ideal central attacking midfielder for Dortmund, but an up-and-down first year under Tuchel and the return of Gotze spell trouble for the fan favourite.

The cup match and the Bundesliga opener described Kagawa well: Scoring a brace against Trier but failing to make an impact against Mainz, the Japan international's second stint with the Black and Yellows has so far been plagued by inconsistency.

Gotze wasn't bought to sit on the bench, and if not against Leipzig, the World Cup winner is going to start before long.

Dortmund need more creativity on the pitch after relying heavily on Ousmane Dembele's running past his marker against Mainz. Schurrle was the most consistent creative force against his former club with no fewer than six key passes, per WhoScored.com. No other midfielder had more than one, and Kagawa had fewer touches of the ball than all his team-mates bar striker Pierre-Emerick Aubameyang.

Of course, Kagawa and Gotze could play together. After all, Dortmund played large portions of last season in a 4-1-4-1/4-3-3 hybrid system.

However, with Weigl only returning to form after the Euros and the back line not yet on the same page despite hugely positive first impressions from Hummels' replacement Marc Bartra, it seems unlikely that Tuchel will field his two No. 10s at the same time for now.

With a long season ahead and the 43-year-old a fan of rotation, especially to fit specific game plans, all players will get their chances, but Castro and Kagawa need to improve if they don't want to wait for theirs once the top dogs take their spots.

Lars Pollmann also writes for YellowWallPod.com. You can follow him on Twitter.