NAGPUR, India (Reuters) Mahendra Singh Dhoni, left with the dilemma of who to bowl the last over in a World Cup thriller with South Africa needing 13 to win, made a brave decision on Saturday and watched it backfire spectacularly.Rather than opt for the impressive spinner Harbajhan Singh, the Indian skipper decided seamer Ashish Nehra was the man to secure the two points the co-hosts needed to secure their place in the quarter-finals with one group match still to play.Within four balls, Dhoni realised he had got it wrong. Very wrong.South African tail-ender Robin Peterson hoisted a six and hit two fours off a shattered Nehra to take his team past their target of 297 and complete one of the most exciting games of a tournament which has already seen its fair share of drama.How India lost this match will take Dhoni and his team-mates a long time to fathom.After 10 overs they were cruising at 87 without loss with Sachin Tendulkar and Virender Sehwag, probably the most potent opening pair of the 14 teams competing here, at full throttle.Even after Sehwag’s departure for 73 in the 18th over, India looked to be heading for a repeat of their score in the opening day of the tournament, 370 against Bangladesh.Tendulkar, the little master, continued apace after his partner’s exit, rolling on inevitably to a 99th international century, his 48th in a one-dayers and a sixth in the World Cup.When he was out for 111, attempting one majestic lofted off drive too many, India were sitting very pretty on 267 for two with just over 10 overs still left to pile up a daunting score.Later, South African fast bowler Dale Steyn conceded that his team were expecting to chase at least 340 but the Indian middle and lower order batsmen failed to follow that script.Instead no less than nine wickets counting Tendulkar’s clattered for just 29 runs with Steyn collecting final figures of five for 50.Suddenly, a broken team took to their dressing room with a spring in their step, believing what had appeared to be a lost cause an hour earlier was now a very achievable run chase.South Africa, who had fallen short of overhauling England’s total of 171 in their previous match, looked for the majority of their innings as though the Indian target would be beyond them. Just.Hashim Amla (61), Jacques Kallis (69) and AB De Villiers (52) all threatened to tilt the balance in their team’s favour before they were dismissed just at the wrong time for them.Harbhajan (three for 53) was responsible for the demise of Amla, De Villiers and JP Duminy as a bowler and Kallis as a fielder with his accurate throw from the deep outpacing the all-rounder.With one over to go, South Africa looked destined to fall marginally short with the main hopes on Peterson, their spin bowler who has already made an impact with the ball at this tournament but is hardly recognised for his hitting prowess.He proved himself, however, ultra cool in a very tight spot as Nehra instead succumbed to the pressure.The first delivery of the final over was glanced perilously close to Peterson’s leg-stump for four but the next was met with the full face of the bat and it sailed over the boundary ropes for a huge six.Peterson scrambled two from the next delivery and as Dhoni brought his field in with one needed for victory, savagely cut the hapless Nehra for a match-winning boundary.The result leaves this most competitive of groups on something of a knife-edge though both these teams should still comfortably progress to the last eight.India are still top on seven points with one to play against the West Indies. The Caribbeans and South Africa have two more games left and are on six points with England on five points and Bangladesh on four.Ireland have two points and two games to play and could also yet qualify. They must play South Africa next, however, and Smith’s team now very much have momentum in their favour.