to simply "Pääjärvi," and that he will wear the jersey number 91. On 23 September, in his first pre-season game with Edmonton, Pääjärvi scored a hat-trick and registered an assist for four points as the Oilers defeated the Tampa Bay Lightning, 5–2. On 7 October, Pääjärvi made his NHL regular season debut against the Calgary Flames. He then scored his first career NHL goal nine days later, on 16 October, against Flames goaltender Miikka Kiprusoff. Pääjärvi finished his rookie season with 34 points, finishing sixth on the team in scoring. In the 2011–12 season, after recording three points in 25 games and having sat-out as a healthy scratch for six games, Pääjärvi was assigned to Edmonton's American Hockey League (AHL) affiliate, the Oklahoma City Barons. During the 2012–13 NHL lockout, Pääjärvi remained with Oklahoma in the AHL. When play resumed in January 2013 for the 48-game 2012–13 season, Pääjärvi played in 42 games, scoring nine goals and seven assists for 16 points, while also spending further time during the season with the Barons. St. Louis Blues On 10 July 2013, Pääjärvi was traded, along with a second-round pick, to the St. Louis Blues in exchange for left winger David Perron. Later in the off-season, on 2 August, Pääjärvi signed a two-year, $2.4 million contract with St. Louis. On 29 December 2014, the Blues placed Pääjärvi on waivers and, upon clearing, was assigned to St. Louis' AHL affiliate, the Chicago Wolves, where he remained until the end of the 2014–15 season. Prior to his demotion, he had played in ten games, registering just one assist. Following the 2014–15 NHL season, Pääjärvi became a restricted free agent under the NHL Collective Bargaining Agreement. The St. Louis Blues made him a qualifying offer to retain his NHL rights and, on 5 July 2015, Pääjärvi filed for Salary Arbitration. Pääjärvi spent the majority of the 2015-16 season with the Blues, appearing in 48 games. Pääjärvi also skated in three playoff games. 2016-17 saw Pääjärvi have more of an even split, playing 32 games for the Blues and 26 for the Wolves. Again, Pääjärvi suited up for the Blues during the playoffs, scoring one goal and two assists. Ottawa Senators On 25 January 2018, the Blues placed Pääjärvi on waivers, where he was claimed by the Ottawa Senators the following day. Pääjärvi finished out the season with 12 points in 79 games. On 30 May