Minnesota Vikings As a
dual-threat quarterback, Armstrong sought to join the
National Football League (NFL) by changing positions. Prior to the
NFL draft, Armstrong converted positions to
wide receiver. Armstrong was not invited to the
NFL Combine and, despite attracting interest during Nebraska's pro day, was not drafted in the
2017 NFL draft. Armstrong was subsequently given a tryout with the
Minnesota Vikings as a
running back, but was later asked to sign as a
safety, a defensive position and one he had not played since high school. Armstrong was not signed by Minnesota following his early May tryout but later signed with the Vikings as a safety on May 30, 2017. He was waived by the Vikings on June 16, 2017.
Your Call Football In May 2018, Armstrong signed with
Your Call Football.
Salt Lake Stallions On September 9, 2018, Armstrong announced via his
Twitter account that he had signed with the
Salt Lake Stallions of the
Alliance of American Football for the 2019 season. However, he went unselected in the
2019 AAF QB Draft.
Nebraska Danger On January 2, 2019, it was announced that Armstrong had signed with the
Nebraska Danger, an
Indoor Football League team based in Grand Island, Nebraska. Armstrong's first game was a victory, in which he threw 8 completions on 12 attempts for 158 yards and four touchdowns, while also rushing for 23 yards and another score on three attempts. Armstrong was named the IFL Offensive Player of the Week for his performance in his professional debut. Armstrong played in all 14 regular season games for the Danger, leading them to a playoff berth, finishing with a 7–7 record in 5th place. Armstrong completed 150 out of 251 passes, for 1,799 yards and 37 touchdowns against nine interceptions, was the league leader in rushing yards and rushing touchdowns, with 137 attempts for 720 yards and 26 scores (both single season team records), and served as the holder for field goals and extra points. On June 21, 2019, Armstrong led the Danger to a 45-40 playoff win over the Green Bay Blizzard before suffering a 62–45 defeat at the hands of the
Arizona Rattlers. During the playoffs, Armstrong completed 23 of 35 passes for 189 yards and six touchdowns against two interceptions, while also rushing for 63 yards and four more scores. Armstrong was named the Indoor Football League Offensive Rookie of the Year for 2019.
Sioux Falls Storm On October 17, 2019, Armstrong signed with the Sioux Falls Storm.
Omaha Beef For the 2023 season, Armstrong signed with the Omaha Beef. He would lead the Beef to their second league title in three seasons and their first perfect season in franchise history. On November 10, 2023, Armstrong re-signed with the Beef for their first season in the
National Arena League (NAL). During the
2024 NAL season, Armstrong again lead the Beef to an undefeated championship season, being named NAL Player of the Year. Armstrong announced his retirement from football on August 7, 2024, citing impending surgeries. After sitting out the 2025 NAL regular season, Armstrong came out of retirement to sign with the Beef ahead of their 2025 playoff game, helping the Beef return to their fifth championship game appearance in five years. ==Coaching career==