Rory McIlroy is heading for a first-round showdown with Ernie Els at the Accenture Match Play next Wednesday following the withdrawal of the injured Paul Casey from the first World Golf Championship of 2012.

Casey has not recovered from the shoulder injury he sustained while snowboarding in Colorado during his winter break, but he still hopes to play in the Cadillac Championship in Doral in three weeks' time.

The Englishman's replacement, world No 66 George Coetzee of South Africa, will make his World Championship debut against global No 1 and defending champion Luke Donald in the first round, provided there are no further withdrawals.

Donald and fellow Englishman Justin Rose both made a satisfactory start to the Northern Trust Open yesterday with one-under-par 70s in difficult conditions at Riviera CC.