The two squared-off earlier this month at UFC 264 and Poirier was adjudged the winner after Notorious broke his ankle while trying to step back from a punch.
McGregor was thus rendered unable to continue and his opponent won the fight via doctor's stoppage.
The defeat saw the Irishman drop two places to ninth in the lightweight category in the newly released UFC rankings.
Poirier remains at the top following his win which is his third on the trot. He is behind lightweight champion Charles Oliveira.
Justin Gaethje is yet to have a fight following his defeat to Khabib Nurmagomedov but he remains second in the lightweight rankings followed by Beneiil Dariush whose victory over Tony Ferguson in May marked his seventh in a row.
Michael Chandler is at No.4 followed by Islam Makhachev who rose four places to fifth following his victory over Thiago Moises last weekend.
The Russian's recent victory sees a few fighters drop places, including Ferguson and Rafael dos Anjos who are currently sixth and seventh respectively.
Dan Hooker remains at eighth while Gregor Gillespie completes the top 10 of the UFC lightweight rankings.
McGregor has lost four of his last five fights which sees him in what's his lowest position for a while. The Irishman seems to be out of touch and many have been of the opinion that he should retire.
McGregor has vowed to return strongly but his ankle injury will keep him out for a while. UFC president Dana White did say that a fourth fight between him and Poirier could take place once he recovers.
It will be interesting to see when Notorious is back in the Octagon but reaching higher up in the rankings seems difficult for him, particularly with the likes of Makhachev around.