The Brazil international was forced off in the 13th minute of his side's 1-0 victory at Vicarage Road and was later seen with heavy strapping on his thigh.
Manager Jurgen Klopp confirmed that he had suffered a dead leg but said he was hopeful that the problem was not more severe.
Coutinho later offered an update of his own via his official Instagram page, writing: "Thanks for all the support. It isn't serious."
Liverpool's win, which came courtesy of Emre Can's spectacular overhead kick in first-half stoppage time, allowed them to consolidate third place in the table and take a big step towards Champions League qualification.