The pair faced off yesterday as Liverpool won at Craven Cottage, with Babel getting on the scoresheet.
"We speak regularly, for example, we talk about our careers. We are also good friends," said Wijnaldum.
"I am glad to see him again, but unfortunately he plays for the opponent."
He added: “I see how focused he is to play well and to score. He is very important to the national team and I also think he is very important to Fulham, given the way he plays."