KTP won 2-1 against Haka at the weekend in a battle for survival, condemning Haka to automatic relegation and giving themselves another chance to stay up, and were looking to take momentum from that result as they travelled to Turku.
They would have fancied their chances as TPS had failed to win any of their last four matches in the second tier, costing them automatic promotion, which was taken by champions Lahti.
Yet it was the home side who had the better of the chances in a goalless first half, before they were given a huge boost just before the hour mark when KTP's Felipe Aspergren was sent off for a second bookable offence.
And TPS made their man-advantage count 12 minutes from time, when a deep cross from Aly Coulibaly was headed goalwards by Albijon Muzaci. Oscar Linner made the save, but Muzaci stayed alert to fire home the rebound.
Things got better for the Turku side in the 85th minute, when a corner was cleared only to Coulibaly at the edge of the area. His neat touch brought the ball down for Onni Helen to sweep into the net with pace.
Two minutes later, TPS were in dreamland when they caught KTP on the counter-attack and worked the ball wide to Miika Kauppila on the left, and his cross was on a plate for Helen to nod past the helpless Linner.
The 3-0 victory has given TPS every chance of returning to the top flight for the first time since 2020. The teams will meet in Kotka for the second leg on Sunday.
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