The Liverpool medic reached for his microphone, a brief message filtered through to the dugout, assistant manager Pep Lijnders let out a cry of frustration.
And just like that, inside a bubbling Villa Park, Fabinho's night was over, Jurgen Klopp's best-laid plans hit a snag and even a brilliant, battling victory carried a small asterisks.
Liverpool march on, their hopes of a Quadruple still alive. Somehow. Alas, only time will tell if a casualty suffered here will come back to bite at Wembley, even Paris.
'We cannot just push players through all the time,' the Liverpool boss had warned before this game, No 59 of a punishing season.