The 23-year-old has put in a string of masterclass performances at the heart of the Royals backline to add weight to his claims for a permanent spot in the Double Winners first team.
The Gunners face a crisis in the centre of their defence with only Pascal Cygan and Sol Campbell fit to play.
However, England defender Campbell received his marching orders as his side slumped to a defeat at Southampton. He will now face a three match ban, starting on December 7th.
Arsenal travel to Old Trafford to play Manchester United on the 7th and with Martin Keown unlikely to be fit to make a first team return Arsene Wenger may be forced to recall Upson to partner Cygan at centre-back.
Reading play top-of-the-table Portsmouth on December 7th so would dearly like to retain the former England Under 21 man's services for the duration of his loan spell.
The Gunners have the option to recall Upson at any point should they require him.
Reading have yet to receive a call from the Gunners so the former Luton Town man should play in tomorrow night's clash with Crystal Palace at Smellhurst Park.