On one hand, Sahin's first call-up to the national team since 2014 is indicative of how quickly the 27-year-old has found his form after missing almost an entire year due to a somewhat mysterious tendon irritation. On the other hand, Tuchel would surely have preferred keeping his midfielder in Dortmund.
The Black and Yellows have been very careful with their No. 18, slowly bringing him up to speed during a busy schedule with a lot of midweek fixtures.
Sahin came back with a bang, as Tuchel thrust him directly into the starting lineup in the first leg of the UEFA Europa League round-of-32 tie with Porto on February 18. YellowWallPod.com's Luca Gierl was one of many Dortmund supporters who didn't see it coming:
Luca Gierl @LucaGierl
Nuri Şahin is starting. Think that gave me a minor heart attack.2016-2-18 17:03:25
The Turkey international surprisingly didn't show any rust after 355 days without a game, as left-back Marcel Schmelzer astutely pointed out on Instagram after the game: "The boss is back."
Sahin indeed bossed the middle of the park against the Portuguese giants, as the compilation put together by tactics blogger Tom Payne shows:
The 27-year-old took it all in, telling the club's official website after the game: "I had a long spell out with a lot of setbacks during my rehabilitation. But it was all worth it for this evening. It was fantastic."
Since then, Sahin has featured in five more games, starting three. He's yet to play a full 90-minute match, but that's to be expected after this long an absence.
Tuchel promised his midfielder an important role in a press conference in February, as Dortmund-based football writer Stefan Buczko relayed:
Stefan Buczko @StefanBuczko
Tuchel: "From all I've seen, Sahin will play an extremely important role for us. I cannot stress enough how prominent his role will be."2016-2-5 11:41:37
It will be interesting to see whether the 42-year-old will actually makes good on that promise, however. Sahin's performances have been fine, but there might not be a place in the first-choice starting XI for him anytime soon.
Twenty-year-old Julian Weigl has been a true revelation this season and, after a short drought, has found his stride again in recent weeks. The Germany under-21 international resembles Barcelona's Sergio Busquets more with each game, as he's recently started to dribble his way out of tight spots more regularly.
Sahin and Weigl have played together, but it feels like they're too similar to work next to each other, especially as the games get more important in Dortmund's hunt for trophies in all three competitions.
Both midfielders like to drop deep in the buildup phase, collecting the ball in their own third with the game in front of them. Too often this results in a hole in the middle of the park, as Dortmund lack a player to connect defence and attack.
Neither Sahin nor Weigl can replace "the impetus that [Ilkay] Gundogan so ably provides," as Lewis Ambrose pointed out in a piece for YellowWallPod.com. "The Turkish international is an excellent passer and creates space well but cannot open and exploit gaps while running with the ball at his feet."
With that in mind, Sahin doesn't fit the bill as a potential replacement for Gundogan, whose departure from Signal Iduna Park seems like a matter of time—he could be off as soon as this summer if he doesn't extend his contract, set to expire in 2017.
No, Sahin's place in Dortmund's squad seems to be at the base of midfield, and it's hard to see him overtake Weigl in that role.
The 27-year-old, of course, still is very valuable for Tuchel, especially because of his passing range in buildup play, but injuries have taken a toll on Sahin, who doesn't have the athleticism and quickness to regularly play in an advanced role.
He'll pick up a lot of games if he stays healthy and be an important figure off the pitch as well, thanks to his experience—even negative lessons he learned during disappointing spells at Real Madrid and Liverpool—but it's hard to envision a scenario in which he'll be locked in as a regular starter.