Albie Morkel will be monitored overnight after suffering lower back spasms during the Proteas' ICC World Twenty20 warm-up match against New Zealand.
Morkel scored an unbeaten 15 runs off four balls to lift South Africa to a commanding score of 186, but was only able to bowl nine balls before leaving the field in Colombo.
"He [Morkel] first felt the pain when he hit the six while he was batting, but he thought that it was something minor," Proteas team manager Dr Mohammed Moosajee said on Monday after South Africa's nine-run victory.
"He aggravated it while he was bowling and came off as a precautionary measure to receive treatment from our physio, Brandon Jackson … We will see how he does overnight; if he doesn't improve substantially by tomorrow [Tuesday] morning he will have to have an MRI scan."
New Zealand won the toss and sent the Proteas in to bat after the start was delayed due to a damp pitch, and South Africa captain AB de Villiers anchored the innings, guiding them to 186/6 in their 20 overs.
In reply, the Black Caps were restricted to 177/8 as Steyn picked up three scalps in one over, returning 4/25 and securing a win for his side.
The World T20 tournament starts on Tuesday when hosts Sri Lanka face Zimbabwe in Hambantota.
South Africa, playing in the same group, square up against Zimbabwe in their opening match in Hambantota on Thursday. – Sapa