One of the allures of the Champions League Twenty20 is the chance it gives for the little guy on the big stage. None of the obscure domestic cricketers grabbed the opportunity as dramatically as 25-year-old Arun Karthik. He thwacked the final ball of the match over midwicket to conjure a preposterous win, which took Royal Challengers Bangalore through to the semi-finals, and set off on a memorable chest-thumping celebration. That will be the abiding image of Royal Challengers' victory over South Australia, and perhaps of the league phase of the CLT20.

There was another moment to define the game though. It was in the 13th over of the chase, in the middle of an audacious counterattack by Virat Kohli and Tillakaratne Dilshan. Kohli punched the air angrily after drilling a full toss to long-off for a single. After completing the run, he chastised himself and practised the off-drive again. Annoyance at missing out on a hit-me ball is one thing, but Kohli had missed out on the fourth ball of the over after striking the first three for six, six and four. It was that sort of a match, where no amount of runs seemed enough.

Kohli had played a couple of blinders for the Royal Challengers in the CLT20 last year, and was second only to Chris Gayle in amassing runs in the IPL this season, but this 36-ball 70 ranks as his finest Twenty20 innings. There were several challenges to deal with in this high-pressure must-win game: no IPL team had ever beaten an Australian side in the CLT20, only a handful of times had a target in excess of 200 been successfully hunted down, and finally Gayle, the man whose form has closely mirrored that of the Royal Challengers this year, had been dismissed relatively cheaply.

After Gayle and Dilshan had provided the initial thrust, Kohli came out and utterly dominated the high-octane century stand with Dilshan, which kept the chase on course. Of the first 74 runs of the partnership, Kohli's contribution was 61, a big chunk of which came off his favourite Twenty20 stroke - the inside-out lofted drive in the arc stretching from long-off to deep extra cover. There were dabs past third man for four, hard-run twos after tucking the ball softly towards the deep, and no ugly across-the-line heaves were attempted.

By the time Kohli was dismissed, the pair had taken Royal Challengers to 165 for 2, with an eminently gettable 50 needed off the final five overs. "We were pumped up, to want to play like me and Dilshan did, you need some sort of adrenaline," Kohli at the post-match press conference, with the sound of the Royal Challengers celebrating still being heard. "I was really excited since we were hitting the sixes at the right time and probably the best T20 match of my life."

Still to complete the job after Kohli's dismissal, Royal Challengers needed some amazing hits and most of their batsmen delivered. Saurabh Tiwary bludgeoned Tait for a 99-metre six over long-on, Mayank Agarwal pummelled his first ball over the extra-cover boundary, Daniel Vettori flicked one way beyond midwicket, and S Aravind played an immensely courageous scoop in the final over for four. Despite all that, it came down to nine off three balls, at which stage Kohli says he lost hope.

"I didn't (think we could win)," he said. "I was sitting with the coach and we needed seven off two, and I told him, 'coach if we get four off this ball, and two off the last ball, just run, I think we are going to make it,' when we got a single, I just closed my eyes, and said coach whatever happens, happens."

Then came Karthik's moment of magic, and the crowd went berserk. The Royal Challengers were also delirious, mobbing Karthik, who couldn't stop bouncing up and down after the match-sealing six. Kohli, an animated presence in the dug-out since his dismissal, charged out and was the first to pluck some stumps as souvenirs. "None of us can still believe that, especially since it was a quarter-final for us, to be able to play like that was a team's delight, a coach's delight, a player's delight, all in all a wonderful experience."

Royal Challengers may have emphatically proven they can win without Gayle turning in a headlining performance, but their shoddy fielding and toothless bowling remain a cause for worry. For their fans and the team, those concerns can wait for another day as they savoured a famous win.

Siddarth Ravindran is a sub-editor at ESPNcricinfo