Arsenal fear Kai Havertz has suffered a significant hamstring injury amid growing speculation he could miss the rest of the season, sources told ESPN.
Havertz, 25, is set to undergo further tests in the next 24 hours to determine the full extent of the problem sustained during a training session on the club's midseason training break in Dubai, United Arab Emirates.
The squad landed back in London on Tuesday and Havertz is now being assessed, with manager Mikel Arteta set to provide an update at Friday's news conference ahead of their weekend Premier League trip to Leicester City.
However, sources say the Gunners believe Havertz has suffered a significant setback and concerns are growing that the forward could be sidelined for a long period.
That would represent a major blow to Arsenal, as it would leave them without a recognised striker given Gabriel Jesus has already been ruled out for the rest of the campaign following knee surgery.
It will also renew scrutiny over their decision not to sign a striker in the January transfer window.
Arteta admitted the club were short of attacking options and voiced his disappointment at missing out with sources confirming the club opted not to pursue a deal for Aston Villa's Ollie Watkins after having a £40 million ($49.8m) bid rejected.
Longer-term targets including Benjamin Sesko at Red Bull Leipzig and Newcastle's Alexander Isak were not available.
Arteta had described Havertz as a genetic "powerhouse" after the window closed when asked if he could compensate for Arsenal's failure to sign a forward.
