If surprise had an expression, it would look like Leon Johnson when the first delivery of Dale Steyn's third over got big on him and brushed the edge of his bat, like Shivnarine Chanderpaul when he crouched down to evade a bouncer but did not get his hands low enough and exposed his gloves or like Marlon Samuels when extra bounce induced a leading edge. Strangely, it wasn't the aggression that caught West Indies off guard, it was the athlete at the other end.

"We didn't expect Steyn to bowl this morning," Denesh Ramdin, West Indies' captain admitted. And it showed.

West Indies were left stunned by a show only Steyn, when he is in the mood, can stage. Unlike day three, when he was still sussing out the situation, stalling on his speed and seeing whether the cramps he was experiencing would allow him to bowl any more, Steyn returned revving on the fourth morning. His pace was up, his intensity sharp and his angry eyes were darting about. It was as though Steyn had somewhere else to be on Saturday afternoon, because he led South Africa in finishing West Indies off in 80 minutes and 15.3 overs, but it was actually that he discovered how best to operate exactly where he was: SuperSport Park.

Steyn had watched his new-ball partner Vernon Philander find the right formula on the surface the previous day: a touch full, just outside off, which is actually where Philander bowls most of the time anyway. He had four wickets to show for his consistency and Steyn had none.

Come Saturday morning, he had corrected that. Steyn greeted Johnson by finding his bottom edge and by the end of over had beaten him as well. "At slip, we could feel from the ball that he quickened up. When he beat the left-hander, we got the feeling things were going to happen pretty quickly," Hashim Amla said.

After flirting with a fuller length for the first two overs he bowled to Johnson, Steyn held it back a touch when he began the third. The resulting rise found the edge and allowed it to carry. Immediately, Steyn strategised on how best to use a shorter length and trialled it successfully against Chanderpaul. He began his first over to him with a delivery identical to the one that got Johnson but Chanderpaul was ready for it. He left it alone. Then Steyn went length and Chanderpaul edged him for four. Chanderpaul perhaps expected a length ball again, but Steyn fired a bouncer on his body.

"I have a routine about how I use the bouncer," Steyn said. "I thought he figured I'll go length so I decided I'll just bomb him again and get it a bit straighter." Chanderpaul had not been expecting it and although he got down in time, his hands did not. Steyn's had opened West Indies up and only needed to plough through.

He went back to a fuller for Samuels, and knew the job was almost complete. "Chanderpaul and Samuels are two of the big players for them. That's not to say the rest of the guys can't contribute but we know those are the two big wickets and once we get that there is a feeling of ease," Steyn said. "On this surface, it's a matter of time before you can get out any batsmen, not just their batsmen. But once you've got those two, with the rest, if you just land it there enough times you are probably gonna come right."

The short ball got rid of Ramdin, who had a particularly disappointing game as a leader after gifting the part-time spinner Dean Elgar his wicket in the first innings, and the tail. Ramdin said he wants to see his men show "more application" when confronted with it. "We need to be more disciplined and stay away from short balls," he said. "I hope we can lean as fast as possible, including myself. It's very difficult to get starts on these pitches, so when we do, it's important that we carry on."

But Steyn seldom allows opposition to settle sufficiently enough to make that possible and he enjoys the angst he causes along the way. "I love taking wickets; I love getting into players' heads," he said. "Give me a red ball, I am just going to bowl. I like to get the people out, it doesn't matter whose batting on the other side just give me the ball. I love playing Test cricket."

Especially on days when he is rewarded as handsomely as he was today.  "Sometimes you go past the edge, sometimes you find it and when you do find it, you are making batters play a little bit more. Yesterday I felt I was okay but the ball found the bat and went into the gaps. Today, I was a little bit more consistent. I didn't deserve the wickets yesterday, I deserved them today."

Firdose Moonda is ESPNcricinfo's South Africa correspondent