The unassuming medium pace of the portly Smith produced 18 dot balls out of the 24 he bowled – the most by any bowler in this year’s tournament – as the Knight Riders' batsmen crashed and burned just when they needed a big performance to cement their place in the playoffs.
Captain Gautam Gambhir (8) began the slide when confusion with Robin Uthappa allowed Shadab Jakati to produce a brilliant run out with a direct hit from short mid-wicket but Smith claimed the next four wickets to fall.
Manish Pandey edged to Lions skipper Suresh Raina at slip for a single before Uthappa edged to wicketkeeper Dinesh Karthik for 25 from 19 balls.
Piyush Chawla’s surprise promotion to No 4 backfired when Smith hit the top of middle stump for 11 from 16 balls and Shakib al Hasan (3 from 8 balls) uppercut a long hop to third man.
Left-arm spinner Jakati had Suryakumar Yadav caught in the deep for 17 and the Knight Riders plunged to 120 for seven when top scorer Yusuf Pathan drove a full toss from Dhawal Kulkarni to deep cover.