The shock decision by the United Arab Emirates to quit OPEC blindsided its partners of six decades. Now the cartel will have to fight to stay relevant in a fast-shifting global oil market.

Officials from other member countries were left stunned on Tuesday, as longstanding tensions between Abu Dhabi and the group¡¯s de facto leader Saudi Arabia culminated in the sudden announcement that OPEC¡¯s third-largest producer will exit in a matter of days.

For OPEC and its partners, the departure will dilute their ability to manage oil prices by adjusting supply, while positioning the UAE as a wild-card player ¡ª and one that has long chafed against the constraints imposed by OPEC quotas ¡ª at a time of unprecedented upheaval in the global market.