2004-05: Riku Helenius split the season between Ilves’ U-18 and U-20 squads and was one of the top goalies at Finland's Young Lions camp for potential future national team players. He played two games with the U-20 squad with a GAA of 2.77 and .914 save percentage. In 16 games with the U-18 squad, he had 3 shutouts and a 1.99 GAA. Helenius allowed 15 goals in five playoff games for the U-18 team.
2005-06: Helenius had a dream season both with Ilves' U-18 and U-20 teams and playing for Finland in international competition. In 26 games with the Ilves U-20 team, he had four shutouts with a 2.68 GAA and .919 save percentage. Helenius allowed seven goals in two U-20 playoff games. Helenius allowed two goals in two games fur the U-18 team during the season but was hot for them in the post-season as Ilves won the U-18 title. In five games, he allowed 13 goals and finished with a 2.60 GAA. Helenius bolstered his reputation as a prospect with his play in the WJC U-18 tournament in Sweden. He was named the tournament's Best Goalie – starting all six games for silver-medal winning Finland and finishing with a 1.83 GAA and .943 save percentage. He stopped 45 of 47 shots against the USA in a 3-1 loss in the gold medal game.
2006-07: Helenius was expected to assume the starting role for the Ilves U-20 squad but suffered a season-ending shoulder injury that required surgery after playing in just two games. Following the season, he was selected by the Seattle Thunderbirds of the WHL in the first round (46th overall) of the 2007 CHL Import Draft.
2007-08: Helenius had a good showing in his first year of North American hockey. Playing in a tandem with Jacob DeSerres (PHI) with Seattle, Helenius went 22-12 with 3 shutouts and 6 OT losses and had a 2.42 GAA and .920 save percentage. Helenius played in 9 of 12 playoff games for the Thunderbirds and was 4-5 with a 2.70 GAA and .911 save percentage. Seattle defeated Kelowna in seven games in the first round before falling to Tri-City in a five-game, second-round series. Helenius' Team Finland experience at the WJC U-20 tournament was not as enjoyable as the U-18 squad's run in 2005-06. He recorded a shutout but was 2-2 with a 3.36 GAA and .864 save percentage as Finland finished sixth.
2008-09: Few players have spent as much time in as many different uniforms in one season as Helenius did in his first year of pro hockey. After attending camp with the Lightning, Helenius was assigned to Tampa Bay’s ECHL affiliate Augusta but the Lynx would cease operations 18 games into the season. He was then loaned to the Mississippi Sea Wolves but saw action in just three games between December 12 and December 17 behind starter Ryan Munce. In eleven ECHL games between the two teams, Helenius was 4-5 with 2 OT losses with a 3.80 GAA and .896 save percentage. Having played just seven games in two months, Helenius joined the Lightning's AHL affiliate Norfolk on December 21 but did not see his first action until January 2 – relieving Norfolk starter Mike McKenna in the third period of a 6-1 Lightning loss to Worcester (Helenius stopped 11 of 12 shots while also picking up a slashing minor). Helenius, after being sent back to Mississippi but not playing, was promoted to the Lightning and made his NHL debut in a January 30 loss to the Flyers. He played almost seven minutes in relief of Mike Smith and stopped both shots he faced as Tampa Bay lost, 6-1. Helenius was returned to Norfolk where he saw consistent action for the remainder of the season, albeit on a team that wasn't very good. In his first start since December 17 when he was with the Sea Wolves, Helenius made 41 saves in a 3-0 shutout win over Bridgeport on February 6. He then started 23 games down the stretch for Norfolk, finishing with a record of 9-15. In 25 games with Norfolk, Helenius finished with a 2.72 GAA and .918 save percentage. Helenius was loaned to the Elmira Jackals for the ECHL playoffs and was visibly fatigued. In his one start against Trenton in the first round, he allowed 6 goals on 38 shots in a 6-5 Elmira loss. He then relieved Michael Teslak midway through the second period in an Eastern Conference semifinal game against Cincinnati and allowed four goals on nine shots.
2009-10: With veteran Antero Niittymaki signed by the Lightning over the summer, Helenius was assigned to Norfolk and spent the first half of the season with the Admirals before being loaned to Sodertalje in the Swedish league. He started just one game in October for the Admirals as Dustin Tokarski started 6 of the first 7 games. Helenius enjoyed his best string of the season in November, winning 4 of 5 starts and three times holding the opposition to one goal. The offensively-challenged Admirals then hit the skids, losing 7 of 9 games and Helenius was winless in four starts. Helenius' final win with the Admirals came in his next-to-last start, a 5-4 win over Manitoba on Dec. 12. Helenius was recalled to Tampa Bay on December 26 and served as Mike Smith's backup while Niittymaki's wife was having their second child but was returned to Norfolk without seeing any action. In 12 games with the Admirals, Helenius was 5-7 with a 2.75 GAA and .896 save percentage. Helenius, as did former Lightning goalie Karri Ramo, seemed to rediscover his game by returning to Europe. In the regular season, he was 4-2-2 with a 2.42 GAA and .923 for a Sodertalje team which finished 11th in the 12-team Elitserien. In the 10-game Kval series to avoid relegation to Sweden's second division, Helenius was 6-3 including a 2-0 shutout over Rogle and had a 2.74 GAA.
2010-11: Helenius appeared in 18 games for Sodertalje in Sweden's Elitserien as a backup to Pontus Sjogren. He finished with a 3.03 GAA and .884 save percentage as Sodertalje was 11th in the 12-team league. Helenius played in five Kvalserien (Relegation) playoff games and had a 2.13 GAA and .914 save percentage. Helenius signed a contract offer to play with JyP in Finland's SM-Liiga in 2011-12 in May and was tendered a qualifying offer by the Lightning in June 2011.
2011-12: Helenius made a successful return to Finland – skating with SM-Liiga champion JyP. After splitting the goaltending duties with veteran Joni Myllykoski during the regular season, he started 13 of 14 games in the playoffs as the Jyvaskyla club won its second Kanada Cup in four years. In 33 regular season games he was 17-9-5 with 7 shutouts and had an SM-Liiga-leading 1.64 goals against and .936 save percentage. Helenius was 11-2 in 13 playoff games and had a 1.73 goals against and .947 save percentage. Helenius signed a two-year contract with Tampa Bay in June, 2012.
Helenius is a big goalie who plays a conventional butterfly style. He has excellent movement in all directions, and relies on filling the net with his huge frame when the puck is in close. His reflexes and speed are good. He is adept at using his long legs to block or direct pucks in a manner of which few goalies are physically capable. Helenius' glove and blocker techniques have developed slower than the rest of his game. He likes to be active with the puck but can get himself into trouble at times by being overly aggressive. After enjoying nothing but success at the junior level, Helenius' confidence and mental game, particularly his calm nature, seemed to take a hit with the lack of activity and adversity in his first two pro seasons.
Helenius has signed a contract with the Tampa Bay Lightning and will play in North America in 2013-14.