He will also lose out on $18,145.17, per WFAN 660's Sean Hartnett.
The incident occurred during the first period of Monday night's game between the Blues and Sharks when Reaves dumped the puck into the Sharks' zone in front of Tennyson. The San Jose defenseman got to the puck in the corner first and was hit hard from behind by an onrushing Reaves.
Tennyson's head first made contact with the glass before he went down. He stayed there for quite some time, as seen in the video below:
Reaves isn't in the NHL for his skill, as he's only scored 19 goals in his first six years in the league. The 6'1", 224-pound winger has built his reputation on the Blues' fourth line as being a physical instigator in order to get under the opponent's skin.
He's had 116 or more penalty minutes in three of the past four seasons, but 2015-16 has been a down year in that department. Entering Monday night, he had just 25 penalty minutes before racking up 15 minutes against the Sharks after the hit.
Yet this is the first time in his career that the league has suspended him. The NHL fined him over $3,000 earlier this season for a thrown elbow at Los Angeles Kings forward Anze Kopitar, but its discipline ended at that.
Boarding has been an issue in the NHL, and the league has tried to crack down on offenders with suspensions and fines. When a player is facing the boards with his back turned to the play, he is in a vulnerable position.
A hit from behind, especially one with the ferocity and speed that Reaves exhibited, usually results in injury, as the boards don't give much.
Tennyson did not return to Monday night's game, and a timetable for his return has not been released yet. The Blues, though, will be without Reaves' sparkplug qualities for three big games against the New York Rangers, Nashville Predators and Carolina Hurricanes.
The Rangers and Predators are both playoff teams in their respective conferences, while the Hurricanes have won four of their last six games. Luckily for the Blues, their 79 points have them placed comfortably in a Western Conference playoff spot.
St. Louis could turn to Dmitrij Jaskin to play right wing on the fourth line. The 22-year-old has three goals and seven assists in 49 games with the Blues this season.
Stats courtesy of Hockey-Reference.com.