Jennings played high school football and basketball at Westerville South High School, where he was a first team All-League player as a senior. From 2010 to 2013, he played for the Cardinals at Saginaw Valley State, where he threw for 10,710 yards and 96 touchdowns at the Division II program. As a senior, Jennings threw for 3,824 yards for 30 touchdowns, additionally rushing for 470 yards and 12 touchdowns.
In April 2015, Jennings was signed by the BC Lions of the CFL. He competed for the back-up quarterback position on the depth chart, which he received in the season opener. 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 quarterbackTravis 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 touchdownpass 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 coachWally Buono announced that Jennings would enter training camp as the #1 quarterback on the depth chart 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.
