JYP began the day in fourth, two points clear of Ilves and the rest of the chasing pack, so whatever the result in Jyvaskyla, it was sure to have a big effect on the race to seal an automatic place in the quarter-finals.
John Nyberg's strike for Ilves in the eighth was the only goal of the first 20 minutes, but the home side only needed two minutes of the second period to get back on level terms through Jere Lassila.
Teemu Engberg and Samuli Ratinen gave the Lynx their second and third leads of the game, respectively, but each time JYP hit back, first through Valtteri Ojantakanen and then Juuso Puustinen early in the third period.
But when Peter Quenneville put the Tampere side 4-3 ahead with just over five minutes left, there was no fourth reply from JYP, as Lukas Jasek finally gave his side breathing space with an empty-netter, before Matic Torok made it 6-3 for good measure in the final minute.
Four wins on the spin have put Ilves into fourth, while JYP have fallen out of form at just the wrong time, with one win in four.
Falling behind in the race for fourth were Lukko, who were on the end of a 6-2 defeat by Tappara, as the leaders ensured they would finish the regular season in first place for the fourth time in the last five seasons, and secured Champions Hockey League qualification.
Two goals from Oiva Keskinen helped Tappara build a 3-0 lead that they were rarely in danger of surrendering, as they moved onto 116 points, seven clear of their nearest challengers with two matches to play. Successive defeat for Lukko keeps them in sixth, but now three points off fourth.
KooKoo have joined Tappara and SaiPa in securing a top four finish, and have moved into second for now at least, after cruising past Jukurit 5-1, a result that ends the visitors' playoff ambitions.
Jukurit needed to win their last three to have any hope of qualifying, but that dream was all but over after 13 minutes, as goals from Akseli Makinen and Veeti Miettinen put KooKoo in a commanding position.
Jesper Ahlroth added a third approaching the midpoint in the match, and though Joona Mutka got Jukurit on the board, Jiri Parssinen quickly restored the three-goal lead, before Robert Rooba added KooKoo's fifth late on. It's a first win in three for the hosts, and successive losses for Jukurit.
Pelicans have guaranteed that they will be playing postseason hockey this season, as they came from 2-0 down at home to Hameenlinna to take the game to overtime, but after no goals in the extra period, Joona Kumpula scored the winner in the shooutout to win 3-2.
The Lahti side moved 11 points clear of TPS Turku, who missed the chance to go above Hameenlinna and into the final playoff place as they fell 6-2 to Assat. Three Nestor Noiva goals settled a second win in three for the Pori side, while TPS are now two points behind HPK.
The point for Hameenlinna meant Karpat's slim playoff chance was over before their match at IFK Helsinki was over, but in the end it didn't matter as they were beaten 3-1, a result that sees HIFK join Assat, Kiekko and Pelicans of being assured of the place in the wildcard round.
Kiekko-Espoo hammered Vaasan Sport with a 7-0 win at home that saw the scoring was opened and closed by a brace for Arvid Aronsson, as KE remain in ninth after three wins in a row, while it's 49 losses from 59 for Sport, who only forced Sami Rajiniemi to make eight saves.
Follow the climax to the Liiga regular season on Flashscore.