Yobo, 34, is a free agent and can join the Gunners outside of the transfer window. So could Diego Lugano, who was awful at West Brom last season. Either could be remembered less fondly than Kim Källström.
You may remember him from such clubs as Everton and Fenerbahçe
With the cumbersome Laurent Koscielny and Per Mertesacker supported only by tonsilitis-suffering Calum Chambers at centre-back, Wenger started rookie Héctor Bellerín at right-back in Dortmund. Nacho Monreal is sidelined while Mathieu Debuchy is facing three months out with an ankle injury.
Lugano remembers the time he defended someone for biting an opponent
Another option is Lassana Diarra, who spent about six months at Arsenal in 2007-08 before leaving to win a trophy at Portsmouth.
More - or less - encouragingly for Gooners, is that Wenger is supposedly keen on Barcelona's Pedro. Pedro is more inspiring than the aforementioned trio but is your archetypal Arsenal player; skilful, lightweight and unlikely to make a difference.