The Reds are facing a huge tie in the Champions League if they wish to progress to the quarter finals.
And Wijnaldum knows that getting past Diego Simeone's Atletico will be no easy task.
The Reds face the first leg on Tuesday at the Estadio Metropolitano.
"They are a lot like us, fighters. They are a team more or less like us, also really difficult to beat," the Netherlands international told UEFA.
"I think you can see that in their playing style in the competition. They are always battling to get results and they can easily switch at times when it is necessary, they know what they have to do to win the match.
"So yes, these are going to be really difficult matches."