Form of Mats Hummels, Return of Nuri Sahin Fuels Borussia Dortmund in Porto Win

When Borussia Dortmund goalkeeper Roman Burki saved the only true goalscoring opportunity FC Porto mustered all game in Thursday's UEFA Europa League round-of-32 match at Signal Iduna Park, a shot from substitute striker Suk Hyun-Jun in the 89th minute, it was more than a 'keeper doing his job.

It meant the Black and Yellows would keep their fourth clean sheet in six games in 2016 after only keeping nine in 30 attempts during the first half of the season.

Fans were a bit sceptical about Dortmund's defensive prowess despite their good record in the new calendar year—understandably so, considering the Ruhr side didn't exactly play against offensive powerhouses in the Bundesliga.

But the complete annihilation of Porto's attack—granted, the Portuguese giants were negative all evening long—showed the Black and Yellows have improved drastically on the sometimes all-too-shambolic showings of the Hinrunde, as the first half of the season is called in Germany.

One man signifies that improvement more than anyone else: Mats Hummels.

The club captain was often criticised during the Hinrunde, during which he strung together awkward performances filled with individual mistakes and positioning errors.

In 2016, however, the 2014 FIFA World Cup winner is in outstanding form. He played arguably his best match of the entire campaign in the Bundesliga game at Borussia Monchengladbach on Jan. 23—until Thursday, that is.

Sporting director Michael Zorc almost prophetically told German sport magazine Kicker's Thursday edition the skipper is in fine form at the moment, adding that he's ever present on the pitch both offensively and defensively.

Hummels mastered his responsibilities in both build-up play and defence to perfection against Porto, earning a 10/10 rating from ESPN FC's Stefan Buczko, who said: "His tackles are clean, but his cutting forward passes are filthy good. He's as great to watch as he is effective for his team."

The 27-year-old benefited greatly from a tactical wrinkle from head coach Thomas Tuchel, who, when asked about his side's improved defensive performance in recent weeks, said, per the club's official website: "Perhaps we have simply become more alert after everyone spoke to us about it. I am very happy about it, it's really not something you can take for granted."

In possession, Dortmund reverted to three at the back, with Hummels playing at left-back. He interpreted that role offensively, as YellowWallPod.com's Luca Gierl noted after the game:

The Black and Yellows positioned themselves high up the pitch and also stretched the field horizontally, which would've been a huge gamble just a few weeks ago. It probably only worked because of the surprising return of Nuri Sahin.

The Turkey international came from the proverbial nowhere to start his first game in 355 days, but one wouldn't have known judging only his performance.

He was in total command in midfield, hardly putting a foot wrong or misplacing a pass. He and Hummels orchestrated Dortmund's build-up play, as the video put together by tactics blogger Tom Payne below shows:

Tuchel was ecstatic after the game: "It is really quite something to come back after such a long break and perform like that on the pitch. He is always alert, passes well, is intelligent and has a good instinct for spaces where we have numerical superiority. It was great to watch."

Sahin's surprising return to the field is a huge boost for Dortmund's rest of the season.

We recently wrote he "will be rusty after a full year out of action and won't be close to his full capacity until next season, most likely," but we'll gladly accept being wrong on this one.

It's a mouthwatering prospect that the club could field a midfield trio of Sahin, Julian Weigl and Ilkay Gundogan in the coming weeks. They'd go a long way in protecting their side from counter-attacks, simply because they so rarely lose possession.

With Hummels on his best run of form since the 2014 World Cup and Sahin celebrating a glorious return from a lengthy injury absence, not to mention the 2-0 advantage they have in their bag, Dortmund can look forward to Thursday's return meeting at the Estadio do Dragao.

Lars Pollmann is a Featured Columnist writing on Borussia Dortmund. He also writes for YellowWallPod.com. You can follow him on Twitter.