Right-back Bellerin and young Brazilian Martinelli have missed recent games with hamstring injuries, but could be fit for the clash at the Emirates.
He is expected to be absent for a period of six to nine months and joins Kieran Tierney on the sidelines, although the ex-Celtic left-back is aiming to return to full training in March after successful surgery on his dislocated right shoulder.
Leeds boss Marcelo Bielsa is expected to make changes after the New Year's Day draw at Championship promotion rivals West Brom.
Barry Douglas may deputise for left-back Ezgjan Alioski, who came off at half-time at the Hawthorns, and teenage goalkeeper Illan Meslier hopes to make his debut.
Versatile youngster Robbie Gotts could also finally get his debut after been named on the bench 32 times in the Championship since Bielsa's arrival in 2018.