Karunaratne is certainly leading from the front as he has occupied the crease for 190 minutes, but the left-hander is putting away the bad ball effectively as he has collected 17 fours off 116 deliveries.
With Sri Lanka trailing by 145 runs on first innings and losing master blaster opener Kusal Perera for just a single in the third over, bowled through the gate by a beautiful Lungi Ngidi delivery, it has been important for Karunaratne to keep the scoreboard ticking over.
Niroshan Dickwella is with him on 18*.
South Africa’s inexperienced attack endured a flat period as Karunaratne and Lahiru Thirimanne (31) added 85 for the second wicket following the dismissal of Kusal, and it took a big moment of good fortune for the Proteas to shift the momentum.
Thirimanne, who had played a series of superb drives, tried to glance Ngidi off his hip and was caught down the leg side by wicketkeeper Quinton de Kock. Amazingly, Ngidi’s next delivery was similarly off-target but it dismissed Kusal Mendis for a first-ball duck, De Kock taking a stunning leg-side catch diving at full-length. The unfortunate Mendis therefore completed a pair and his third successive duck.
Anrich Nortje then bounced out debutant Minod Bhanuka for one, Keshav Maharaj taking a brilliant running catch off a top-edged hook, and the Proteas attack looked much more threatening in the last hour of the day, but by then the luck seemed to have shifted and several edges went over the slips or through the gaps between them.
South Africa had begun the second day on 148 for one, just nine runs behind and with both Dean Elgar, on 92, and Rassie van der Dussen, on 40, approaching milestones.
Elgar reached the landmark of three figures first, notching the second-fastest of his 13 Test centuries as he got there in 133 balls, with 18 fours. Van der Dussen went to his half-century off 98 deliveries and the pair passed South Africa’s record second-wicket partnership against Sri Lanka (125 between Elgar & Faf du Plessis in Galle in 2014) and then also broke the Wanderers record of 182 set by Andrew Strauss and Rob Key for England back in 2004/5.
Elgar scored the couple of runs that took the partnership to 184, but he was dismissed by the next delivery, Dushmantha Chameera bowling a fine delivery that just nipped away a touch to find the edge of the left-hander’s bat. Elgar was caught at first slip for 127, ending four hours of quality batsmanship in which he showed a tremendous ability to bat fluently, absorb pressure and then lift the scoring rate again.
The wicket of Van der Dussen followed in the next over, Sri Lanka needing good use of the review system to confirm the 31-year-old had gloved a paddle-pull down the leg side off Dasun Shanaka, wicketkeeper Dickwella scrambling to take the catch.
Sri Lanka then quickly ran through the rest of the Proteas batting, the last nine wickets falling for just 84 runs as they were bowled out for 302, left-arm swing bowler Vishwa Fernando leading an excellent bowling comeback with five for 101, his maiden five-wicket haul.
He was well supported by skilful seamer Shanaka and feisty debutant Asitha Fernando, who took two wickets each.