The factory Ducati rider and his Gresini counterpart on a year-old Desmosedici were battling over fifth in the closing stages of Sunday’s 25-lap grand prix in Portugal.
Marquez launched his GP23 up the inside of Bagnaia on lap 23 but ran slightly wide having moved ahead of the factory Ducati.
As he cut back to try to defend the position, Bagnaia came back up the inside and the pair collided.
Both riders crashed as a result of the contact, with Marquez remounting to finish 16th while Bagnaia retired in the pits moments after the tangle.
The collision was placed under review by the MotoGP Stewards Panel, but it deemed it a racing incident and no punishment was apportioned.
The collision marks the first test for Ducati in how it manages its roster since Marquez signed for Gresini.
What will make Ducati’s situation trickier is the fact Marquez is not directly contracted to the manufacturer.
Bagnaia is now 23 points behind Portugal GP winner and Pramac Ducati rival Jorge Martin, having thrown a sprint win away on Saturday due to an error late on.
Marquez is now 27 points off the championship lead, with his first podium on the Ducati in the sprint on Saturday softening the blow to his position in the standings.
More to follow
