Arsenal defender Jurrien Timber is reportedly facing months on the sidelines with an anterior cruciate ligament injury sustained in Saturday's win over Nottingham Forest.
The Netherlands international's Premier League debut was cut short after just 50 minutes at the Emirates, as he went down on his own early in the second half of the match.
Timber had previously clashed with Brennan Johnson late on in the opening period and required treatment - while being booked for his troubles - but he nevertheless emerged for the second half.
However, while in control of the ball, Timber appeared to jar his knee and dropped to the turf in pain, before being helped off the field by Arsenal's medical staff.
Takehiro Tomiyasu replaced the stricken Dutchman as Arsenal clung on for a 2-1 victory, and Timber hinted on social media that his injury was not a serious one.
The official diagnosis is less promising, though, as Dutch publication De Telegraaf claims that Timber has damaged his ACL and could now be out for the next few months.
It is unclear whether Timber has suffered a full rupture - which could keep him out for most if not all of the campaign - or if the 22-year-old's issue is a less severe one, as Arsenal fans eagerly await an official update from the club.
The decision to send Timber out for the second half of Saturday's game drew criticism, but Mikel Arteta insisted that both the player and medical team were happy for him to continue.
The ex-Ajax man only arrived in North London this summer and had produced a strong display in his side's pre-season fixtures, as well as their Community Shield win over Manchester City.
Timber filled in at left-back in Arsenal's first two competitive fixtures of the season due to Oleksandr Zinchenko's calf problem, which he is yet to fully recover from.
The Ukrainian was beset by problems in that area during his debut campaign with Arsenal, although he was able to enjoy a brief cameo role in a recent charity game before re-entering the Arsenal treatment room.
Arteta is confident that Zinchenko's problem will not keep him sidelined for too much longer, but it remains to be seen if he will be able to return for next Monday's London derby with Crystal Palace.
With Timber and Zinchenko sidelined, either Tomiyasu or Kieran Tierney would be expected to fill in at left-back for Arsenal, although the latter was not even named in the squad for the win over Forest.
The Scotland international is still thought to be on Newcastle United's wishlist for a possible summer transfer, but the Magpies are yet to agree a fee with Arsenal.
