Dustin -- who's still recovering from that WAR with Dan Hooker over the weekend -- is now the #2 ranked UFC lightweight, right behind Khabib and Justin.

Poirier has fought both of 'em already -- he beat Justin in 2018  but lost to Khabib in 2019.

Now, with Justin and Khabib squaring off at UFC 253 on Sept. 19, Dustin's in a pretty solid spot to fight the winner.

Dustin knows there are no guarantees in the UFC ... but he's convinced a Gaethje victory would put him in a much better position for a title shot.

"It’s more of a guaranteed lock for me to fight for the belt is Justin wins," Dustin says.

"I'm the last guy to beat him. I'm the only guy still in the organization who beat him. So it would make a lot of sense. And, I know he wants that fight as well."

So, how can Justin stop the seemingly indestructible Dagestani champion?

Dustin's got some ideas ...

"If Justin can keep his back off the fence, I believe he can out-scramble Khabib in the open."

"He just has such a pedigree in collegiate wrestling and that open mat area is going to be where Justin shines in the wrestling."

"If Khabib can get him against the fence, I believe Justin will be in trouble but we’ll see if he can stick to the game plan."

"I would assume that's gonna be his game plan -- to stay in the middle, make Khabib wrestle in the open and throw big punches."

And, if Khabib wins, Dustin says he's already been thinking about how he can correct the mistakes he made in the first fight and get the "W" in the rematch ... if Dana White gives him the shot.

There's more ... Dustin also told us about his plans to auction off his fight gear from the Hooker fight to help the less fortunate.

Good stuff.