Pelicans had lost their previous two, but it took less than four minutes for an upset to be on the cards when Daniel Nieminen put them ahead. Heading the first-period shot count 14-6, the Lahti side were good value for their lead, which they deservedly doubled in 15 minutes in through Einari Luhanka.
Nieminen was in the thick of the action four minutes into the second period, too, but this time he was guilty of holding, and it took just eight seconds of the resulting powerplay for Joachim Blichfeld to pull a goal back for Tappara.
Back on the ice, Nieminen was on hand a minute later to restore the two-goal cushion, combining with Oskars Batna to set up Joona Kumpula, who made it 3-1, and Pelicans looked out of sight nine minutes into the third, as Batna added another assist, finding Onni Kayhko, who added number four.
But the Battle Axe began to wield in the final five minutes - Kristian Tanus scored with 04:07 left in the game, then added a second when deflecting in Aleksi Matinmikko's strike from the point to make it 4-3 with still over two minutes left.
Pelicans, though, held on for a key three points that lift them to 10th, five points clear of those outside the playoff places. Tappara remain four points clear at the top and face the challenge of top-four chasing KalPa next up.
Those three points were even more significant for the Lahti club after Hameenlinna beat KalPa 2-1 after penalties on Wednesday night.
Thomas Caron scored the opener in the shootout for the hosts, and that was the only effort to find the net to give HPK a second win in a row and take them within two points of the postseason places. KalPa remain fifth after only closing the gap to Lukko to two points.
Jukurit have not given up hope of reaching the top 12 after they won a thriller of a six-pointer 5-4 at home to Karpat. The hosts remain 15th, but now only a point behind the Oulu side and seven short of IFK Helsinki in 12th place.
Karpat were on course for a third win in four as they raced into a 3-0 lead in the first 20 minutes, only for the Mikkeli side to dominate the second, which ended with Karpat 4-3 ahead.
In the third period, Eemeli Saari and Jeremi Tammela turned things around in the first five minutes, but the visitors had no response, and Jukurit held on for an unlikely first win in three.
