Fast, 25, skated in 68 games with the Rangers this past season, registering six goals and 15 assists for 21 points, along with a plus-six rating and 16 penalty minutes. He was named the winner of the Players' Player Award in 2016-17, which is given annually to the Ranger who, as selected by his teammates, "best exemplifies what it means to be a team player." Fast posted a plus/minus rating of even or better in 53 of the 68 games he played during this past season, including a plus-one rating or better in 20 contests. He ranked third among Rangers forwards in hits (99) and ranked fourth among Blueshirts forwards in blocked shots (44) in 2016-17. Fast skated in his 200th career NHL game on February 13, 2017 at Columbus.

The 6-0, 190-pounder also skated in 12 games with the Rangers during the 2017 Stanley Cup Playoffs, registering three goals and three assists for six points, along with a plus-four rating. Fast established playoff career-highs in several categories during the 2017 Stanley Cup Playoffs, including plus/minus rating, shorthanded goals (one), shorthanded assists (one), and shorthanded points (two), and he also tied playoff career-highs in goals, assists, and points. He led the NHL in shorthanded points, and tied for the NHL lead in shorthanded goals and shorthanded assists in the playoffs. Fast led the Rangers in shorthanded points, tied for the team lead in shorthanded goals and shorthanded assists, tied for third in plus/minus rating, tied for fourth in goals and points, ranked fifth in hits (33), and tied for sixth in assists in the playoffs. He also led the Rangers with five points (two goals, three assists) on the road in the playoffs.

Fast has skated in 216 career NHL games over parts of four seasons (2013-14 - 2016-17), all with the Rangers, registering 22 goals and 43 assists for 65 points, along with a plus-nine rating and 44 penalty minutes. During the 2014-15 season, the Rangers won 13 consecutive games in which Fast played from December 8, 2014 vs. Pittsburgh to January 10, 2015 at San Jose, and he became the first Ranger to be on the winning side in 13 straight games in one season during the NHL's modern era. He has received the Players' Player Award in each of the last two seasons (2015-16 and 2016-17), and he is one of 11 Rangers in franchise history who have won the award in at least two consecutive seasons. Fast established career-highs in games played (79), goals (10), assists (20), points (30), and plus/minus rating (plus-nine) during the 2015-16 season, and he recorded all of his 30 points during the season at even strength. The Rangers have posted a 128-69-19 record when Fast has been in the lineup in his career (.637 points percentage).

The Nassjo, Sweden, native has also skated in 39 career NHL playoff games, all with the Rangers, registering six goals and eight assists for 14 points, along with a plus-three rating and two penalty minutes. Fast made his NHL playoff debut during the 2014 Stanley Cup Playoffs, and he tallied one assist in three contests while helping the Rangers advance to the Stanley Cup Final. He established playoff career-highs in games played (19), goals (three), assists (three), and points (six) while helping the Blueshirts advance to the Eastern Conference Final during the 2015 Stanley Cup Playoffs. Fast registered two goals in Game 3 of the Eastern Conference Final at Tampa Bay on May 20, 2015, and he became the first Rangers rookie to register two goals in a road playoff game since Mike Ridley during the Patrick Division Semifinals against Philadelphia in 1986.

Fast was selected by the Rangers in the sixth round, 157th overall, of the 2010 NHL Entry Draft.