Smith, who was set to miss the one-day series in Australia and fly home after the third Test to inject his own blood on his injured right elbow, was surprised by a Mitchell Johnson delivery and was struck on the knuckle on his little finger.

The left-hander ran a single to complete his 30 runs before leaving the field in obvious pain. The X-rays showed a break in the fifth metacarpal and he is unlikely to bat in the second innings.

Smith returned from hospital to the dressing room later in the afternoon with his left hand in a cast.

According to South African team management, a stand-in captain will be decided before the second innings. With vice captain Ashwell Prince also out with a hand injury, wicketkeeper Mark Boucher is the leading candidate to skipper the side which is searching for a historic series whitewash of Australia.

Smith will meet with the team's medical specialists in Pretoria next week to plan his recovery from both injuries and get ready for the home Test series against Australia, which starts on February 26.