"He has scored many goals against me. Too many!" Oblak said in an interview with Sky Sports.
"But he is a great player, an amazing player, the best player. There are many times that he scores a goal and you have this feeling that you cannot understand how he has scored so easily.
"You are not even close. Sometimes it feels like he has just passed the ball into the goal, it is not even a shot."
Lionel Messi has scored ten goals against Oblak since the Slovenian has been at Atletico Madrid, but in their most recent meeting, Oblak came out on top, as he kept a clean sheet.
However, the Slovenian did not dwell too much on it, instead choosing to keep the focus on Messi's genius.
"He is still the best player in the world," Oblak said.
"It is strange. Sometimes you think you are controlling [Barcelona], you are controlling him but in a second, he changes the game, he scores a goal, and Barcelona win," he said.
"Sometimes you do not see him. Maybe you are thinking it is not dangerous, and then he scores. This happened to us last season. You need to be 100 percent concentrated."
Jan Oblak says it is difficult to tactically stop Lionel Messi
Oblak said that it is difficult for goalkeepers and defenders to set up against Messi because of the Argentine's varied strengths and unpredictability.
"Normally, goalkeepers, we are shouting all the time to help the defenders but I know it is difficult when Messi is on the other side. The defenders do their best but it is difficult to do anything tactically to stop Messi because you never know what he is going to do.
"All you can do is play hard and when you see him don't leave him. Try to steal the ball but don't give a foul close to the goal because he is great at free-kicks. He is great at everything.
"If you are too close he will go past you. If you are too far he will shoot. It is not easy to decide how you will defend against him because of his unpredictability. It is impossible."
Oblak has been described by his Atletico Madrid boss Diego Simeone as the Lionel Messi of goalkeeper, and it is an accolade that the Slovenian does not take for granted.
"If your coach says that it can only means good things," he said.
Oblak's Atletico Madrid currently lead La Liga on goal difference from Real Madrid but have two games in hand over their city rivals.
Published 24 Dec 2020, 16:34 IST