Jurgen Klopp made a decision in Liverpool's 1-0 defeat by Chelsea on Thursday.
Simply, he took off Mohamed Salah.
The decision was instantly met with confusion from Liverpool fans on social media, as Salah left the Anfield pitch shaking his head.
The Egyptian's agent meanwhile posted a cryptic full stop on Twitter to further fuel the fire.
A number of football pundits have now had their say on the substitution, with the decision being labelled "silly", "surprising" and "concerning".
And Klopp has been given some advice by none other than Jermaine Pennant, who suggested Klopp was wrong to even think about substituting a "player of that stature".
He told Stadium Astro: "I'm concerned that you’re bringing him off. You don't bring off a player of that stature.
"Not because he's bigger than the club, but because what he can do on the pitch. He can produce magic, we've seen that every season that he's played for Liverpool.
"He can be quiet for 80 minutes and bring out one piece of magic when they need it. In a game like this, you should always have Salah on the pitch.
"Bringing on Jota, great substitution. If they would have had Firmino, Jota, Mane and Salah on the pitch, they would have put Chelsea on the back foot even more. Taking him off, I was baffled. You should always keep Salah on the pitch. You can't bite your nose to spite your face.
"Taking him off was silly. If he was on the pitch, who knows what would have happened? I think Klopp needs to be more reasonable than that, I think it was a silly decision."
It's important to note that Pennant points out Salah isn't bigger than the club, but at the same time, the suggestion is Klopp made a huge error of judgement taking off the forward because of who he is.
Perhaps he did on this occasion, but the idea that Klopp cannot take players off in the future because they've previously produced moments of magic is a dangerous one.
Bowing to player pressure is the quickest way to lose a dressing room, and it's not something previous successful managers would put up with.
"The minute a Manchester United player thought he was bigger than the manager, he had to go," wrote legendary Red Devils boss Sir Alex Ferguson in his 2013 autobiography.
"David thought he was bigger than Alex Ferguson. That was the death knell for him."
Klopp was asked for his thoughts on the furore caused by the substitute on Friday and made it quite clear that despite the backlash - and Salah's reaction - he'd do the same again in the future.
"I can't not change a player because it creates a story afterwards. You do it because in the moment you think it's right," said the Liverpool boss.
