After La Chaux-de-Fonds, Olten also puts qualification winners Basel in trouble in the Swiss League playoffs.
Coach Christian Wohlwend's team only lost Game 1 of the best-of-7 semi-final series 2:3 in the 88th minute late on Friday evening.
Olten took the lead at the start of both the first and third periods. Deep into overtime, Vincenzo Küng finally scored to secure a home win for the Baslers, who have 34 more points in qualifying than seventh-placed Olten.
At the end of the first overtime period, the Basel team had already celebrated the supposed victory, but the puck had only crossed the line half a second after the end of the period. Olten, on the other hand, missed the golden opportunity to win on the road in the 75th minute when Basel goalie Andri Henauer saved a penalty.
In the second semi-final, Visp managed the first break against Thurgau with a 3:1 win. Thurgau had only scored the final goal three minutes before the end. The series continues on Sunday.