By London correspondent Tony Hughes | Premier League expert with experience of breaking big stories, including exclusives like this
Carl Jenkinson might not play again until 2017 in a major blow to Arsenal, Football Insider sources understand.
The defender has torn the cruciate ligament in his knee and is expected to be sidelined for nine to 12 months.
Jenkinson saw a knee specialist in London on Wednesday, who confirmed the assessment of doctors that he will not play again this season.
In the worst-case scenario, Jenkinson will be out for the rest of 2016 with an injury that requires extensive rest before a long period of rehabilitation begins.
It is same injury suffered by Theo Walcott in January 2014 and which kept the England international out for nearly an entire year.
Jenkinson has ended his season-long loan at West Ham and returned to parent club Arsenal to undergo his rehabilitation.
The right-back got injured just 10 minutes into West Ham’s 2-2 draw against Manchester City last Saturday following a challenge with Sergio Aguero.
Jenkinson had been on the fringes of the West Ham team in recent months after losing his regular starting place, with the Hammers also signing Sam Byram from Leeds last week for that position.
In other Arsenal transfer news, Mathieu Debuchy is weighing up whether to move to Aston Villa or Sunderland after the Gunners reached loan agreements with both clubs.