Garnacho and Mainoo were two of United's bright sparks in a disappointing season in which they finished a worst-ever eighth in the Premier League era
Spin bowlers Ravichandran Ashwin and Muttiah Muralitharan set up the win as the Warriors were restricted to 128 for seven in 20 overs.
Chennai opening batsmen Mike Hussey and Murali Vijay put on 103 for the first wicket without needing to take any risks.
The result was never in any real doubt although there were only six balls to spare when captain Mahendra Singh Dhoni hit the winning runs.
The win earned Chennai a 2.5-million dollar jackpot and completed a notable double after they won the Indian Premier League earlier this year. The Warriors took home 1.3-million dollars.
Yet the Warriors got off to a flying start, with captain Davy Jacobs hitting 34 off 21 balls after winning the toss.
The South African team raced to 39 for no wicket in the first four overs before Ashwell Prince was bowled by Doug Bollinger for six.
Jacobs was out in the next over when he missed an attempted reverse sweep against Ashwin and was leg before wicket.
After that the scoring rate slowed to a trickle. Ashwin, the top wicket-taker in the tournament, took two for 16 in his four overs and fellow off-spinner Muralitharan took three for 16.
Jacobs hit eight boundaries but the rest of the batsmen could only manage five fours and a six between them, with two fours and a six hit by Craig Thyssen off successive balls in the 17th over.
Vijay made 58 and Hussey 51 not out as the methodically chased down the Warriors total.
Vijay, who finished as the tournament’s leading run-scorer, had two let-offs, both from Mark Boucher, the most experienced player in the Warriors team.
The South African Test wicketkeeper missed an edge off Rusty Theron when Vijay was on 15 and fumbled a stumping chance off left-arm spin bowler Nicky Boje when the batsman had scored 34.
Garnacho and Mainoo were two of United's bright sparks in a disappointing season in which they finished a worst-ever eighth in the Premier League era
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