Borussia Dortmund fell short of success again at the weekend when a stubborn Cologne side held them to a 0-0 draw, just one week after Hamburg dealt a similar blow.
What will of course trouble or perhaps instead puzzle most fans is just how Jurgen Klopp's side managed to succumb to such a performance with their best players on the park. Marco Reus was in attendance, peppering the opponent's goalmouth with chances, and so too was Ilkay Gundogan in midfield and Mats Hummels in defence.
Yet there was one player missing from both games. A central midfielder who has returned to the squad and over the past two seasons quietly reestablished his presence on the side.
Nuri Sahin, Dortmund's playmaker, is what was missing against Cologne and Hamburg and is exactly who Klopp must ensure the club don't lose in the coming summer transfer window.
Of course, before Reus signed his contract extension there would have been no doubt over who the club had to spend all their time trying to hold on to. Yet now that they have their star player tied down, Klopp and his backroom staff have to start prioritising the rest.
Although Hummels is often cited as the subject of many transfer rumours throughout the season and Gundogan tends to steal the headlines with his never-say-die attitude in the club's biggest games, it is in fact the Turkish international who is vital to the manner in which Dortmund win games and challenge for trophies.
To put it simply; Sahin dictates the manner in which Dortmund pass the ball around the park, keep possession, and ultimately score their goals.
It's these subtle but significant things Sahin does in the middle of the pitch that are made all too clear whenever Sebastian Kehl or Sven Bender are brought in when the Turkish midfielder is either injured or unfit to play.
The necessity of Sahin's presence for Dortmund to play the way they play so well is evident when either of the lumbering defensive midfielders is thrown in alongside Ilkay Gundogan and often tend to completely disrupt the manner in which Klopp's side attack their opponent.
Rather than the simple, short passing that has become synonymous with Dortmund's attacking style, we often find Bender and Kehl lumping long balls up the park for the likes of Pierre-Emerick Aubameyang to chase in vain.
This isn't the way Dortmund know how to play football, and it certainly doesn't help them win football games.
When we take a look at the stats we quickly notice just how much of a contrast lay in Dortmund's fortunes when Sahin is in and out of Klopp's team.
As we can see from the graphic above, Dortmund's points-per-game ratio in the Bundesliga this season jumps up from just 1.07 per game to 2.16. Suggesting the team have been twice as effective at winning and drawing games since Sahin came back into the side.
Similarly, suggestions that Kehl and Bender negate any Dortmund attack are confirmed when we note that the club score on average 1.28 goals per game when Sahin isn't playing but 2.16 when he is. Clearly pointing out how important the Turkish international is to those first few passes of any play.
Oddly enough Gundogan's presence doesn't seem to hold as much weight, with the average goals per game actually falling when he was in the starting XI this season. In fact, only Reus has a similar and drastic effect on Dortmund's fortunes.
Klopp's team simply need Sahin in their squad if they hope to score goals and pick up points.