Chelsea have confirmed that Emiliano Martinez has undergone successful surgery on a fractured jaw.
The club's official statement says the goalkeeper was injured in a collision during the second half of the 2-0 win at Everton. Hospital assessment established that surgery was required.
Further information after hospital checks
In the initial post-match update, Xabi Alonso said Martinez had left the stadium conscious and was undergoing precautionary tests.
The new statement provides a confirmed diagnosis and the outcome of the operation. Chelsea have not announced a date for his return to training or competitive football.
Any specific absence measured in weeks or months would therefore go beyond the information in the club's update.
Chelsea said they would support the goalkeeper throughout his recovery.
Context from the Everton match
The official match report describes Martinez being injured while dealing with a free-kick midway through the second half.
After treatment on the pitch, he was replaced by Mike Penders in the 70th minute. Penders made his Premier League debut and helped preserve the clean sheet.
Pedro Neto scored both Chelsea goals, one shortly after the interval and the other near the end of normal time.
Alonso's earlier comments expressed confidence in Penders and the readiness of squad members to contribute when required. They did not establish a long-term selection decision.
The latest confirmed development is the successful operation. Further information on Martinez's availability will require another club update.