Leeds Rhinos have confirmed that their half-back Danny McGuire suffered a broken leg in Friday's defeat at Hull.
The Super League champions went down to a fourth successive loss when they slumped 18-6 at the KC Stadium.
X-rays have revealed that McGuire, 30, fractured his fibula when Hull's Liam Watts fell on him during a tackle.
And the Rhinos' star centre Kallum Watkins, 22, faces time on the sidelines with an ankle injury. Its severity has yet to be determined.
Leeds said on Twitter that McGuire would have further scans on Monday.
McGuire and Watkins join veteran prop Jamie Peacock, utility man Carl Ablett and back Ben Jones-Bishop - who are already out for various lengths of time - on the Headingley Carnegie injury list.
McGuire has been at the club since 2001, winning the Grand Final six times.
He has also played for Great Britain and England during a glittering career.