It's 'simple' as Nortje and Elgar put South Africa on top against Sri Lanka

Nortje claimed career-best figures of six for 56 as Sri Lanka collapsed to 157 all out after winning the toss and choosing to bat first on the pace-friendly Wanderers pitch.

South Africa took full control when they reached 148 for one at the close, with opening batsman Dean Elgar scoring 92 not out.

"In the previous Test we bowled maybe too wide and on both sides of the wicket," said Nortje of South Africa's performance in the first Test at Centurion, where they won by an innings despite Sri Lanka scoring 396 in the first innings.

"We tried to make it a bit simpler and get it into the channel (outside off stump), especially on a pitch like this with the bounce," said Nortje.

The plan worked so well that nine of the Sri Lankans were caught in the arc between wicketkeeper and gully before Nortje bowled last man Ajitha Fernando with a full delivery as the batsman backed away.

Sri Lanka's slump came after a promising start.

With Kusal Perera hitting an aggressive 60, Sri Lanka were on course to reach lunch with minimal damage on a pitch which invariably offers assistance to the bowlers on the first morning.

Perera was caught at gully off the medium-paced Wiaan Mulder 20 minutes from the interval, sparking a calamitous collapse from 71 for one to 84 for five at the break.

'The ball was seaming and there was bounce," said Perera, explaining his attacking stroke play, which brought him 11 boundaries. 

"I was thinking any time I could get out. I was thinking if the ball is coming my way I am going to hit it."

The medium-paced Mulder, playing in his third Test, slowed Perera's momentum with a maiden over. 

With the first ball of his next over, Mulder had Perera caught at gully. 

He followed up with the wickets of Kusal Mendis and Lahiru Thirimanne in a spell of three wickets for one run in three overs.

"It is great to have a guy like Wiaan, who can take wickets as well as bowl dot balls," said Nortje, who sent Sri Lanka to lunch on a low note when he had debutant Minod Bhanuka caught at first slip off the last ball before the interval. 

Four wickets had fallen for 13 runs in four overs.

Nortje, who had made the first breakthrough of the match when he had Sri Lanka captain Dimuth Karunaratne caught behind in the tenth over, claimed four more wickets after lunch.

Ajitha Fernando, making his debut, bowled impressively at the start of the South Africa innings, bustling in at a lively pace. 

He had Aiden Markram caught at second slip in an opening spell of one for 14 in seven overs.

But Elgar batted confidently and had solid support from Rassie van der Dussen in an unbroken second wicket stand of 114 which took South Africa to within nine runs of the Sri Lankan total. 

Elgar, who made 95 in the first Test, faced 119 balls and hit 16 boundaries.

Nortje said he hoped South Africa would again make a big first innings total, following their 621 at Centurion.

"I would like us to bat all day tomorrow and maybe into the next day. There's no rush," he said.