The English-based Italian journalist believes Arsene Wenger will look to strengthen in more than one position during this transfer window.
The Gunners are the subject of a striker crisis after injuries to Theo Walcott and Nicklas Bendtner and are widely tipped to delve into the market to add a striker.
And, while Wenger's midfield is overflowing with an abundance of artisans, the Frenchman clearly feels he needs defensive reinforcements, if Marcotti's claims are to be believed.
Speaking on ESPN FC, the Italian-based Marcotti said: "[Arsene] Wenger is looking elsewhere in the team, he's looking possibly at a central defender.
"[Thomas] Vermaelen has had a few offers and really I think he feels that even if Vermaelen sticks around, they are short in central defence."
With Arsenal still firing on three fronts this season, Marcotti believes adding another stopper to the squad can only be on benefit to Wenger.
"They're still obviously in the FA Cup," he added. "They've got the Champions League - they feel that they could use a fourth central defender.
"Remember, Vermaelen hasn't exactly played great when called upon recently, so I think there could be some movement there as well as up front.
Ultimately, though, the goal in this window for the Premier League frontrunners is to shore up their numbers up front and offer some much-needed support to Olivier Giroud.
"A striker remains a priority and, right now, I think he views [Dimitar] Berbatov as the alternative, the fall-back option if he doesn't get the guy he wants."
Arsenal were this week linked with Celtic defender Virgil van Dijk and Anderlecht's Cheikou Kouyate.