Arsenal were dealt a major blow during the first half of their Carabao Cup semi-final second leg after Gabriel Martinelli was forced off with an injury.
Martinelli went down in the 37th minute at St James' Park, with the forward clutching his right hamstring.
Arsenal boss Mikel Arteta immediately signalled for teenager Ethan Nwaneri to come on following the blow.
Martinelli was seen limping off the field, with the Brazilian now appearing set for a spell on the sidelines.
The loss of Martinelli will be another blow to Arteta, amid a series of injuries in attacking positions.