Singh said India were in with a good chance of squaring the three-match series after bowling out South Africa for 131 on a day during which 18 wickets fell for 245 runs.
India were 92 for four in their second innings, an overall lead of 166 runs in the battle between the world's two top-ranked Test nations. Khan and Harbhajan were mainly responsible for the South African collapse. Khan, who missed the first Test because of injury, took three for 36 and Harbhajan four for 10.
The left-armed Khan set the tone by dismissing South African opening batsmen Graeme Smith and Alviro Petersen.
"Zaheer is an experienced guy and it is great to see him taking crucial wickets," said Harbhajan.
"He's been outstanding. It's not just taking wickets, he helps the other bowlers to bowl well. He's the man."
Harbhajan and South African batsman AB de Villiers agreed that the pitch was better than suggested by the scoreboard.
"There's nothing wrong with the wicket, although there is a little bit of extra bounce," said Harbhajan. "When Hashim Amla was going well after lunch batting looked very simple."
Harbhajan's dismissal of Amla for 33, when the batsman missed a sweep and was leg before wicket, sent the South African batting into a spiral in which the last six wickets fell for 35 runs.
"We batted extremely poorly," said De Villiers.
"There were quite a few soft wickets, although they bowled well. But 18 wickets in a day is not a true reflection of how the wicket is playing.
"When India were all out for 205, losing their last four wickets for 22 runs at the start of the day, it seemed that the host nation were set to dominate the match, with conditions for batting expected to ease after an overcast first day.
But Khan and Harbhajan Singh ripped through the South African batting, giving India a first innings lead of 74.
India hurried to 42 without loss in their second innings and looked well on course to avenge their innings defeat in the first Test at Centurion last week.
Then left-arm pace bowler Lonwabo Tsotsobe had Virender Sehwag caught behind for an aggressive 32 at the start of an Indian collapse in which the top four batsmen fell for the addition of 14 runs.
Veteran VVS Laxman and the inexperienced Cheteshwar Pujara restored a semblance of sanity to a frenetic day by batting together for 76 minutes until bad light ended play, adding 36 unbeaten runs in a match in which the best partnership had yielded 43 runs and the highest individual score remained Laxman's first innings 38. Whereas conditions were obviously bowler-friendly on an overcast, rain-shortened first day, the sun shone brightly for most of Monday with a north-easterly breeze blowing across the ground, which normally heralds good weather and favourable batting conditions.
The main hazard for batsmen was steep bounce, while there was some seam movement off a well-grassed pitch.
After Dale Steyn and Morné Morkel wrapped up the Indian first innings, with the last four wickets falling for 22 runs, Khan started the comeback by the number one ranked Test nation when Smith was caught behind and Petersen bowled off his pad.
South Africa then suffered a double blow when in-form Jacques Kallis and AB de Villiers were out in quick succession shortly before lunch.
Kallis, who made a maiden Test double century at Centurion, was run out for 10. He was backing up when bowler Ishant Sharma deflected a drive by Amla into the stumps.
http://www.sport24.co.za/Cricket/IndiaInSA/Harbhajan-hails-Zaheer-20101227
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