Early career Jennings was eligible for the
2014 NFL draft, but went undrafted. He tried out with several
National Football League (NFL) teams prior to the
2014 season, including the
Kansas City Chiefs, the
Detroit Lions, and the
Green Bay Packers. He also tried out with the
Saskatchewan Roughriders of the CFL in April 2014. Jennings was not signed by any NFL or CFL teams in 2014, and did not play football professionally that year. Jennings recorded his first statistic on July 17 against the Roughriders, where he rushed for one yard on a
quarterback sneak. Due to injuries to starting quarterback
Travis Lulay, Jennings played in eight regular season games, starting six, and started in the Lions' lone playoff game. Jennings completed 66% of his passing attempts for 2,004 yards with 15 touchdowns and 10 interceptions. In his second career start, Jennings also caught a 21 yard touchdown pass on a contested catch thrown into double coverage by receiver
Austin Collie on a trick play against the
Saskatchewan Roughriders. In March 2016, Lions GM and head coach
Wally Buono announced that Jennings would enter training camp as the #1 quarterback on the depth chart (above veteran Lulay) and he hoped that Jennings would have earned that title by Week 1 of the
2016 regular season. On May 5, 2016, Jennings and the Lions agreed on a contract extension through the
2018 CFL season. Prior to signing the extension, Jennings would have become a free-agent following the 2016 campaign. Following a less than impressive
2017 season Jennings agreed to restructure his contract for the 2018 season; lowering his initial salary, but adding more on-the-field incentives. Jennings, who continued to struggle to start the
2018 season, was benched in favour of veteran Travis Lulay starting in Week 5. Lulay suffered a concussion and separated shoulder in consecutive weeks, opening the door for Jennings to start for the remainder of the regular season. Despite winning two of the following three games Jennings was once again relegated in favour of Lulay by Week 18. In late November, following the close of the season, Jennings informed the Lions that he would not be re-signing with the team, intending to become a free agent in February 2019.
Ottawa Redblacks On February 13, 2019 Jennings agreed to a one-year contract with the
Ottawa Redblacks for the
2019 season. Jennings began the season as the backup quarterback to
Dominique Davis. Davis missed two games in July which elevated Jennings to the starting role. However, Jennings struggled in both outings, throwing for less than 200 yards combined with three interceptions and only one touchdown. In Week 11 Jennings came in relief of Davis after he threw three interceptions in the first quarter of the game: Jennings completed 16 of 26 pass attempts for 208 yards with one touchdown, but was unable to lead the Redblacks to victory. As Davis continued to struggle, and the Redblacks fell to 3-7, the team chose to name Jennings' as their starting quarterback in Week 13: Despite throwing for 327 yards Jennings and the Redblacks were defeated 46-17 by divisional rival
Toronto Argonauts. Jennings was demoted to third stringer, and closed out the 3-15 Redblacks' season with a three rushing touchdown performance, but his passing statistics for the year were the worst of his career. He was released by the Redblacks on January 23, 2020. ==Career statistics==