2007-08: Mikko Koskinen made his SM-Liiga debut, appearing in one game with the Espoo Blues, and had a strong season for the Blues U-20 team, finishing with a 2.30 GAA and 1.91 save percentage in 20 games while splitting time with Mika Korhonen.
2008-09: Koskinen made the most of his opportunity with the Espoo Blues as a 20-year-old rookie, taking over the SM-Liiga team starting reigns from one-time Flyers' prospect Bernd Bruckler. Koskinen was 17-9-7 with one shutout in 33 games and finished with a 1.91 GAA and .932 save percentage. Koskinen was ranked second amongst European goalie by Central Scouting and was selected by the Islanders in the 2nd round (31st overall) of the 2009 NHL Draft. Koskinen signed a three-year, entry-level contract with the Islanders in July 2009.
2009-10: Koskinen made the move to North America but suffered a hip injury early in the season that required surgery and kept him off the ice until March. In two October games with AHL Bridgeport he was 1-1 with a 2.45 GAA and .902 save percentage. Koskinen returned to the ice with the ECHL Utah Grizzlies in late March and was 6-0 in six regular season games with a 2.50 GAA and .924 save percentage. He played in four playoff games for the Grizzlies and was 2-1 with a 3.49 GAA and .899 save percentage. He finished the season with Bridgeport during the AHL playoffs. After stopping 7 of 9 shots in a relief appearance, he was 1-1 in two starts for the Sound Tigers. He finished the playoffs with a 2.85 GAA and .900 save percentage.
2010-11: Koskinen made his NHL debut in February – one of six goalies to start for the Islanders during the season – and showed the predictable inconsistency of a second-year goalie still getting his bearings in pro hockey. Koskinen struggled in his first start and then stopped 72 of 78 shots in back-to-back wins over Montreal and Pittsburgh. In his final start he allowed 4 goals on 14 shots and was pulled early in the second period the Islanders came back to win the game). Koskinen was sent back to AHL Bridgeport, where he had been the starter most of the year, but suffered a season-ending wrist injury. In four games with the Islanders he was 2-1 with a 4.33 GAA and .873 save percentage. In 36 games for Bridgeport he was 12-22 with a 3.49 GAA and .892 save percentage as the Sound Tigers finished last in the Atlantic Division.
2011-12: Koskinen began the year with Islanders AHL affiliate Bridgeport – appearing in three games – before returning to Finland to play for KalPa Kuopio in the SM-Liiga. He was 0-2 with a 2.82 goals against and .909 save percentage for the Sound Tigers. In 25 games for KalPa, which finished first in the regular season, he was 13-5-4 with 5 shutouts and had a 2.30 goals against and .917 save percentage. He played in six of eight playoff games as KalPa reached the quarterfinals and was 3-2 with 2 shutouts and had a 2.23 goals against and .890 save percentage.
Koskinen’s greatest asset is his size, which he uses to seemingly fill the entire net and he covers a lot of space in the butterfly. He is inexperienced in terms of the number of games played and has not had a lot of international experience – excelling in the SM-Liiga where he ordinarily does not see the booming slapshots or accurate snipers more common in North America. Still learning as a goaltender, he must work to improve his quickness and foot speed. Very good at anticipating chances and setting himself to limit scoring opportunities. Quality teammate who has earned the respect of the veteran players in Espoo.
Koskinen has left Bridgeport to return back to the Finnish Elite League.