Temba Bavuma said he tried to "stay in the moment" as he approached a long-awaited second Test century. But he admitted that he could not entirely quell his emotions.

The South African captain's 171 not out put his team in a strong position on the third day of the second Test against the West Indies at the Wanderers Stadium in Johannesburg on Friday.

A second innings total of 287 for seven gave them an overall lead of 356.

West Indian captain Kraigg Brathwaite said he still had hopes of a West Indian win. "The pitch is still a good one," he said.

Bavuma had to wait more than seven years to reach three figures for the second time.

"I tried to stay in the moment as much as I could," he said. "But when I got to 96 or so the crowd's energy started picking up in anticipation. My emotions also started picking up."

He scored three singles to get to 99. Then came a delivery from Alzarri Joseph.

"I got a ball outside my stumps and went for it."

The shot flew off the middle of his bat over cover and raced to the boundary.

A small crowd rose to give him a standing ovation.

After reaching three figures off 192 balls, Bavuma went on to 171 off another 83 deliveries. He hit 20 fours.

"It has been a long journey," Bavuma told journalists. "There have been a lot more downs than ups. I keep learning about myself and try to take everything in my stride, to keep my chin up and stay true to myself.

"I've got a lot better understanding of myself and the pressures and challenges that come with international cricket."

Bavuma, 32, made his first hundred in his seventh Test and his eighth innings in a high-scoring draw against England at Newlands in Cape Town in January 2016.

He played in another 48 Tests and batted in 88 more innings without repeating the feat despite hitting 19 half-centuries.

South Africa's most reliable batsman over the past two years, Bavuma was appointed captain before the first Test against the West Indies – and was out for a 'pair'.

He came in on Friday with his team in trouble at eight for two. He accumulated a 107-ball half-century while partners struggled and succumbed against good West Indian bowling.

Bavuma said the situation helped him take his mind off personal milestones.

"I have become accustomed to situations where I have to absorb the pressure, although I haven't made the big scores. A hundred wasn't the target. It came along the way. It helped a lot coming in in that position."

South Africa were 103 for five, a precarious 172 runs ahead, when Bavuma was joined by Wiaan Mulder, one of several  batsmen yet to prove themselves at top level.

Mulder made 42 in a 103-run partnership which accelerated after Bavuma reached his century. Twenty-one overs between tea and the second new ball yielded 98 runs for the loss of Mulder's wicket.

Simon Harmer made 19 while Bavuma scored freely as the pair added 71 for the seventh wicket.

Brathwaite praised Bavuma: "He played a very good innings. I can't fault the bowlers' effort."

With the pitch not posing any undue problems, South Africa were seeking a big lead, especially as there was concern about the fitness of Kagiso Rabada, one of only two fast bowlers picked by the hosts.

Rabada took two for 19 in 12 overs in the first innings, but did not bowl after tea on the second afternoon and was reportedly suffering from a sore back and perhaps a groin strain.

Bavuma did not provide any details but admitted that Rabada was in the hands of South Africa's medical team.

"They say they'll get him out on the field," he said.