Assat had come unstuck against KooKoo at home 24 hours earlier, and now they have lost back-to-back matches for the first time this season, as IFK Helsinki ended their six-match losing run in surprising fashion.
There were no goals in the capital in a fairly even opening 20 minutes, but in the second period the home side gained the upper hand and took a deserved lead 14 minutes in through teenager Jere Somervuori.
Having waited so long for an opener, the second goal arrived just 12 seconds of play later, as Daniel Makiaho and Vincent Marleau combined to set up Petr Kodytek to stun the visitors. Then, a powerplay early in the third period allowed Otto Somppi to put Helsinki in dreamland.
HIFK were great value for their 3-0 win, having more shots on goal in each period, while goaltender Hugo Alnefelt still had plenty to do, making 20 saves in a memorable shutout.
JYP have moved level on 38 points at the top of the standings, only trailing the Aces on number of three-point wins, as they scored two in both the opening and final periods, cruising to a 4-0 win away to KooKoo, who slip to ninth after failing provide a repeat of their performance against Assat.
A third win in a row for Tappara - this time 4-3 away at Karpat - keeps them in third, while Kiekko-Espoo have dropped to sixth, overtaken by Jukurit, who beat them 2-1, and SaiPa, who thrashed TPS Turku 6-1 on the road.
An overtime winner from Teemu Rautiainen put an end to Hameenlinna's four-match losing run as they beat Pelicans 2-1, while Ilves took up residence in the top 12 with a 5-2 win over KalPa, who lose for the first time in four outings.
After three consecutive overtime losses, Vaasan Sport picked up just a second win in 11 by coming from behind to beat Lukko 2-1. That keeps HIFK bottom of the table, while Lukko drop back to eighth.