The playmaker had to be substituted in the 13th minute of the Reds' win over the Hornets after sustaining a heavy knock to his thigh in the early stages at Vicarage Road.
Jürgen Klopp revealed in his post-match press conference that Coutinho had suffered a dead leg, and the Brazilian then posted a photo on social media confirming the problem 'isn't serious' while congratulating Emre Can on his stunning winning goal.