Gini Wijnaldum admits senior Liverpool teammate James Milner can be a hard taskmaster.

Milner has proved himself to be ultra dependable whenever called upon by Jurgen Klopp to fill a variety of roles during Liverpool's rise to the top in recent years.

"The engine that guy has, it's unbelievable," Wijnaldum told the Football Show on Sky Sports.

"I see it in games and in training. He's non-stop [in training]. When you play against him it's really tough.

"He never stops giving everything, so you have to be 100 per cent concentrated otherwise you will lose to him."