To say that Mario Mandzukic's reaction to scoring Bayern Munich's winner in Plzen on Wednesday was muted might be an understatement.
After nodding home Philipp Lahm's cross, the Croat simply hung his head and walked towards the corner flag as more jubilant teammates came to congratulate him.
David Alaba eventually managed to slap a smile on to the striker's face, but Mandzukic's response was rather tepid for such a fiery personality having scored the goal that put Bayern through to the Champions League round of 16.
Mandzukic isn't the happiest Bayern player right now and it's no mystery why.
In his first season in Munich, the 27-year-old displaced prolific hitman Mario Gomez from the lineup and played a pivotal role in Bayern's treble-winning season. He redefined the striker role with his work-rate and scored the all-important opener in the Champions League final.
But since the arrival of coach Pep Guardiola in July, Mandzukic has been less valued. He's started just 10 of Bayern's 19 competitive matches this season.
In the Champions League, he's only been trusted to start on one occasion—last season he was, when fit, first choice in all but one fixture on the biggest stage in club football.
Especially as of late, Guardiola has preferred to use a fluid attack with Thomas Mueller moving from the wing and into a "false striker" role. The results of this tactical approach have been mixed.
Guardiola, who helped promote Lionel Messi to god-like status by converting the Argentine from winger to striker, has been less committed to the use of a false nine at Bayern than he was at Barcelona.
This may in part be due to his not having a clear Messi-type player at his disposal: The trainer experimented with Franck Ribery in the role during preseason training but has only used Thomas Mueller in the role in competitive matches.
Mario Goetze, used as a striker by Germany coach Joachim Loew, is another option who has not yet been fielded by Guardiola as a false nine.
As one might expect, Mueller has been more prolific in front of goal but given fewer assists as a striker than when on the wing.
In 328 minutes as a center-forward, he's scored four goals and given an assist, contributing to a goal every 66 minutes. When in midfield, he's been directly involved in a goal every 96 minutes, scoring six and setting up five more in 1,061 minutes.
By comparison, Mandzukic (who has always been used as a nine) has scored 10 and given an assist in 1,201 minutes as a striker—on average he contributes to a goal or assist every 109 minutes.
Based on the limited statistics above, Mueller might seem an obviously preferential choice for the striker role. But there is more than that to consider.
Only in the last month has Mueller been used for extended periods as the striker. His statistics in that role are affected by times he's moved into the role when Bayern were already on course to win—most notable are a 28-minute outing against Hannover in the DFB-Pokal in which he scored and assisted after Bayern were 2-1 up, as well as a 15-minute performance against Mainz in which he netted Bayern's fourth goal in a 4-1 win.
On the other hand, he did manage to score the winner against Hoffenheim last weekend—a much, much more valuable goal than the aforementioned—after Mandzukic (who also scored) was withdrawn.
Guardiola has only started Mueller as his striker on four occasions, all of which have come since the beginning of October.
Only three times did the 24-year-old play as the nine for the majority of a match: against Leverkusen, Manchester City and (on Wednesday) Plzen.
Mueller scored against City as Bayern played arguably their best football of the season, winning 3-1. But he was ineffective in 80 minutes against Leverkusen when Bayern were held to a 1-1 draw. In Plzen, Bayern were unable to get on the scoreboard until Mandzukic came on in the 59th minute—and it took him just six minutes to break the deadlock.
With Guardiola having started with a false nine in four of Bayern's last seven matches, the Bavarians, for better or for worse, are trending towards a set-up similar to that the trainer used at Barcelona.
It's too early to judge whether a system with a false nine will, with further practice and refinement, be better than one in which Mandzukic is used as the lone striker. But in any case, the risk faced in isolating Mandzukic is not to be underestimated.
Unlike Mario Gomez, who was more easily discarded, the Croat is a fan favorite for his tireless work-rate and was a key figure in bringing treble glory to Munich. When he plays, he scores.
To bench him is to send a demotivating message to all current and prospective Bayern players that giving 110 percent and passing every competitive test may not be enough.
Moreover, use of a false striker system casts a dark shadow over the future of Robert Lewandowski at Bayern. Although the player is until January legally unable to announce where he will play next season, Bild reported months ago that he has a binding agreement to join Bayern in July 2014 and have stuck to that narrative ever since.
An entirely possible scenario come January is that Bayern will be playing without a classic striker but will have both Lewandowski and Mandzukic under contract for 2014-15: The Pole's move would amount to little more than a transfer for transfer's sake and Bayern would be left with not one but two moody strikers to share time off the bench.
All seems rosy at Bayern now, with the Bavarians having tied Barcelona's record of nine consecutive Champions League wins and drawn level with Hamburg's record of 36 undefeated matches in the Bundesliga.
But nothing is perfect forever, not without change, and Mandzukic's current state is an early warning of the turbulence Bayern may face in the near future.
Guardiola must be careful not only to find the right tactical formula for optimal performance but also to keep his players happy and motivated.