Sahibzada Farhan, Rassie van der Dussen and Salman Ali Agha scored 52, 35 and 44 respectively but they were not enough for the losing side.
Usman Tariq claimed three wickets while Mohammad Waseem Jr, Faheem Ashraf, and Mohammad Amir took two wickets each.
Earlier, Gladiators set a target of 210 runs for United in the playoff match of Pakistan Super League (PSL) season 10.
Playing at Lahore’s Gaddafi Stadium, Quetta won the toss and opted to bat first, scoring 209 runs for the loss of 6 wickets in the allotted 20 overs.
For Quetta, Dinesh Chandimal remained unbeaten with 48 runs, Faheem Ashraf scored 45, Finn Allen 41, Avishka Fernando 32, Rilee Rossouw 16, captain Saud Shakeel 12, and Hassan Nawaz added 6 runs.
From Islamabad United, Ben Dwarshuis and Salman Irshad took 2 wickets each, while Imad Wasim and captain Shadab Khan claimed one wicket each.
The winning team from this playoff will secure a spot in the final. Eliminator 1 between Lahore Qalandars and Karachi Kings will be played on Thursday, May 22.
The loser of the qualifier will face the winner of Eliminator 1 in Eliminator 2 on Friday, May 23. The final is set for Sunday, May 25.
Squads:
