"He batted extremely well," said Sehwag after Gilchrist´s 85 off 35 balls took Deccan to a six-wicket victory with 14 balls to spare.
"The bowlers tried everything - yorkers, full tosses, full length, short- pitched - and everything went for fours and sixes."
There were five sixes and ten fours from the former Australian star as the Hyderabad-based Chargers eliminated the tournament favorites.
It was the first time in five matches spread over two seasons that Deccan had been able to beat Delhi, who posted 153 for eight after being sent in.
That target soon looked easy as Gilchrist went on the rampage, hitting a 17-ball half-century, the fastest in the IPL´s short history.
Deccan captain Gilchrist, who had not played cricket in almost a year since the 2008 IPL, said batting was "a bit like riding a bike, you don´t forget what you have to do, but it´s been a great experience to come back after a year off".
Gilchrist paid tribute to his bowlers and fielders for keeping the pressure on Delhi.
"The guys did a great job to restrict them to 150. The previous three games we´ve been in the same scenario with two overs to go and ended up chasing 170-180."
Gilchrist hit five successive boundaries off fellow-Australian Dirk Nannes in the first over of the Deccan innings.
Herschelle Gibbs was bowled playing a reckless shot against Ashish Nehra in the next over but Gilchrist continued his assault, hitting 15 off an over from Pradeep Sangwan, then 13 off Nehra as the total raced to 56 off four overs.
Tillakaratne Dilshan managed an economical over of off-spin, conceding only three runs but Sehwag was smashed for 25 runs in his only over, including three successive sixes by Gilchrist, one from a free hit following a no-ball.
Gilchrist was third man out when he top-edged an attempted big hit against leg-spinner Amit Mishra to backward point off the last ball of the tenth over with the total on 102. Amid the carnage handed out to the other bowlers, Mishra took three for 19 in his four overs.
Deccan made a great start when Ryan Harris dismissed both Delhi opening batsmen for no runs in the first over.
But Sehwag (39) and Dilshan (65) counter-attacked in a third wicket stand of 85 and Delhi were on target for a challenging total before they lost four wickets for eight runs off the last seven balls of the innings.
Harris finished with three for 27.
Delhi finished top of the log in the round robin stage, winning ten of their 14 matches, while Deccan scraped into fourth place with seven wins and seven losses - a big improvement on their 2008 performance when they finished bottom of the log.
The Chennai Super Kings play the Royal Challengers Bangalore in the second semi-final in Johannesburg Saturday. The final will be in Johannesburg Sunday.
"In Twenty20 cricket you always fancy your chances," Gilchrist said of the final. "In a two-horse race anyone can win."
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