The Storm are yet to officially reveal the news, but are expected to do so on Sunday.
He attempted to play on at the time, and it's unclear if that did any further damage, however, he eventually succumbed to the injury after 28 minutes, with Jeremiah Nanai coming onto the park, Kurt Capewell moving to centre and Valentine Holmes back to the wing for the remaining 52 minutes of a series-opening victory against the Blues.
It's understood Coates will be out for eight weeks with surgery required on the ankle, although could be back in as few as six if there is no fracture.
Unfortunate confirmation that Xavier Coates will require surgery on his syndesmosis injury, club expects him to miss 8 weeks (via @LaraPitt_). Tightrope repair has sped up recovery in recent years - if no fracture most NRL players able to return in the 6-8 week range
— NRL PHYSIO (@nrlphysio) June 11, 2022
It'll come as a major blow for the Storm, who are also battling the long-term injury of Reimis Smith.
Ryan Papenhuyzen is due back in the side next week however for Round 15 and a final push to play State of Origin, which will likely see Nick Meaney move back to the wing and Dean Ieremia keep his spot on the other side of the field, with William Warbrick currently injured and Jack Howarth seemingly unable to gain an opportunity.