The former Gunners favourite expects the proven performer to be a shrewd addition, but has questioned why the Blues did business with a domestic rival
David Luiz will help to return Arsenal to the Champions League says Paul Merson, but questions need to be asked about why Chelsea were prepared to do business with a Premier League rival.
The Gunners moved to lure the experienced centre-half away from their London neighbours on transfer deadline day.
An £8 million ($10m) agreement saw Luiz swap Stamford Bridge for Emirates Stadium.