Per Mertersacker's return to full training offers Arsene Wenger a timely defensive boost, with Shkodran Mustafi set to miss most of Arsenal's festive program through injury.
Gunners captain Mertesacker has not played all season due to a knee injury, but stepped up his recovery by training with his team-mates ahead of Tuesday's Premier League clash with Everton at Goodison Park.
Fellow German Mustafi's arrival from Valencia has helped Arsenal discover a new-found defensive solidity this season - only Tottenham and Chelsea have conceded fewer goals than Wenger's side.
Mustafi could miss up to five matches in the packed upcoming fixture list, after sustaining a hamstring injury in Saturday's 3-1 win over Stoke City.
But Mertesacker may be ready to fill that gap, having progressed from last week's light training with a full session.
He posted on Twitter: "It's been a long road but feels so amazing to be back training properly with the @Arsenal boys again and I feel great!"