Gaethje, 33, is set to face the Brazilian for the lightweight title on May 7 at UFC 274 with the event location still yet to be confirmed.
‘The Highlight’ has been campaigning for a title shot against Oliveira for months.
Gaethje is widely regarded as one of the best 155-pounders on the planet having won two of his last three fights with a loss to Khabib Nurmagomedov sandwiched between wins over Michael Chandler and Tony Ferguson.
But according to Poirier, he may want to focus on his boxing for the entire training camp because the only way he can beat ‘Do Bronx’ is by knocking him out.
“Charles can submit him. Charles can win a decision. He has more ways to win.
“I’m not saying that Gaethje won’t knock him out. Charles is a guy who gets hit a lot. In his last two fights, he’s touched the canvas in both fights, and Gaethje is a guy if he gets you hurt, he usually puts you away.
“He has big power, so if you’re able to get touched, you might not recover. It’s an interesting fight, but Charles has more ways to win.”
The 33-year-old American knows exactly where he went wrong, but congratulated the Brazilian for showing the heart of ‘a world champion’.
He admitted: “I should have done a better job with my footwork.
“Not allow myself to be clinched up as easy and kind of smothered my striking output by getting that close, allowing him to walk forward and just get into that clinch range.
“Obviously second round, I wouldn’t have given up the round like that, I would have maybe tried to use my jiu-jitsu to sweep or submit him. There’s a bunch of stuff.
“I hit him with some good shots. He was more durable than I thought he was going to be. He stayed in the fight, as he did in his fight before that with Chandler.
“He got hit with some big shots, went down, almost got finished and came back to win. Showed the world once again that he has what it takes to be a world champion.”