Nishanth, who is in his second year of U-19 cricket, was among the host of net bowlers at Pakistan team's disposal after it turned up for training 12 hours.
Flower departs after two years in charge during which Lucknow made the playoffs and finished third on both occasions.
Madhwal, an engineer from Uttarakhand, returned sensational figures of 5/5 in 3.3 overs as MI inched one step closer to the IPL summit clash.
In the Eliminator against Mumbai Indians at the M A Chidambaram Stadium on Wednesday night, the crowd persistently taunted Naveen as he prepared to bowl.
LSG omitted attacking wicketkeeper-opener Quinton de Kock from their playing XI and it turned out to be a big blunder.
This was MI's maiden win over LSG in four matches. MI will take on defending champions Gujarat Titans in the second Qualifier on Friday.
Gujarat Titans and Chennai Super Kings will meet in the first Qualifier while LSG will play the Eliminator against the fourth-placed side.
Asked to bat first, Marcus Stoinis hit a whirlwind 89 off 47 balls to power Lucknow Super Giants to a challenging 177 for 3.
LSG now have 13 points from 12 games and are in fourth spot behind Gujarat Titans (16 points), CSK (15 points) and Mumbai Indians (14 points).
On-field umpires Akshay Totre, J Madangopal and TV umpire Yeshwant Barde earned the fans' wrath for a poor DRS call in the penultimate over of the SRH innings.