The Australian holds a two-point lead over Rainey, but is still struggling with a leg injury after crashing in July. The Honda rider held a comfortable 65-point lead in the championship until the fall in practice, which left him with a badly broken leg. Doohan hobbled back for the penultimate grand prix in Brazil, but finished in a disappointing 12th place.
The Yamaha rider won the Sao Paolo event, and on his seventh-place showing in yesterday's practice, Doohan will require a huge improvement to capture his first championship title.
Wayne Gardner, of Australia, who makes his 500cc farewell tomorrow, was third best in practice, followed by Niall MacKenzie, of Britain, and Doug Chandler.
SOUTH AFRICAN 500cc GRAND PRIX (Kyalami) First qualifying times: 1 J Kocinski (US) Yamaha 1min 40.400sec; 2 W Rainey (US) Yamaha 1:40.406; 3 W Gardner (Aus) Honda 1:40.721; 4 N McKenzie (GB) Yamaha Banco 1:40.995; 5 D Chandler (US) Suzuki 1:41.028; 6 R Mamola (US) Yamaha 1:41.113; 7 M Doohan (Aus) Honda 1:41.118; 8 K Schwantz (US) Suzuki 1:41.217; 9 A Criville (Sp) Honda 1:41.510; 10 P Goddard (Aus) Yamaha 1:42.486.Reuse content