Australian allrounder Shane Watson has been diagnosed with a minor calf strain and will be given every chance to prove his fitness for the first Test against South Africa starting on Friday.

However the selectors are to meet later on Sunday to choose a player to put on standby in case Watson is unable to play in the Gabba Test.

Cricket Australia high performance chief Pat Howard said Watson was staying positive about his prospects of playing after receiving the preliminary results of scans.

Watson suffered the injury while bowling his first over of the day for NSW on day two of their Sheffield Shield clash against Queensland in Brisbane on Saturday.

Howard said selectors expected to have a much clearer idea about his availability on Monday or Tuesday.