Regular season champions Lukko were made to work in their home opener, before eventually running out 6-2 winners over Vaasan Sport.
Sport, the lowest-seeded side left in the competition, were holding Lukko at 1-1 approaching the midpoint in the match, after Sebastian Wannstrom drew them level after Henri Ikonen's opener.
But when Patrick Khodorenko put Lukko back in front, it was one-way traffic from then on.
Alex Peters' goal in the final minute of the second period was a blow to Sport, before a game misconduct penalty early in the third against Aatu Aarnio all but sealed their fate.
The Rauma side quickly took advantage with powerplay goals from Steven Jandric and Khodorenko, before Ponthus Westerholm made it 6-1 with five to play. Sebastian Stalberg added a consolation for the visitors.
The first of a possible seven Tampere derbies went the way of second seeds Ilves, who took both the bragging rights and a shutout against reigning champions Tappara, winning 4-0.
All four goals at Nokia Arena came in the second period, with Jens Looke scoring the first in the fourth minute.
Carl Klingberg made it 2-0 with less than two minutes left, before a penalty against Veli-Matti Savinainen proved very costly for Tappara.
On the resulting powerplay, Ville Meskanen and Lukas Svejkovsky scored within 23 seconds of each other in the final minute, to all but wrap up the win with 20 minutes of the match to play.
27 saves for Dominik Pavlat meant the Battle Axe could not find a way back into the match.
After beginning the Playoffs with two losses, SaiPa have now won four in a row as they got their Quarter-Final off to a great start by beating IFK Helsinki 4-1 in the capital.
One goal in each of the first two periods - from Henri Nikkanen and Santari Airola - had put the visitors in a commanding position, before Daniel Makiaho finally got the home crowd on its feet with a goal five minutes into the third period.
But two penalties in quick succession ended HIFK's comeback hopes as quickly as they had begun and Antti Kalapudas took advantage on the powerplay.
Otto Kivenmaki sealed the 1-0 series lead for Lappeenranta side with an empty-net goal late on.
Assat have maintained their 100% record in this season's Playoffs, even if they needed overtime to do so, beating third seeds KalPa 2-1 in Kuopio.
Two tripping calls in quick succession were KalPa's undoing in the second period and Assat wasted little time in using their advantage, taking the lead through Kasper Puutio.
The lead lasted only two-and-a-half minutes - the Black & Golds got back to full strength as Assat received a penalty call of their own, allowing Patrick Curry to restore parity on the powerplay.
No goals in the third period meant a tense overtime period was in the offing at Olvi Areena, and finally a winner came nine minutes into the extra period, when Dylan Fabre and Jonne Tammela combined for Jan-Mikael Jarvinen to give the Aces the win.
Game two of each series will be played on Friday, except for Sport vs Lukko, which will be played tomorrow.