Lorenzen was considered to be among the best prospects eligible for the 2013 Major League Baseball draft, and was ranked as the #52 prospect by Baseball America. He was selected with the 38th pick by the Cincinnati Reds. He signed and made his professional debut with the Arizona League Reds. He also pitched for the Dayton Dragons, Bakersfield Blaze, and the Pensacola Blue Wahoos during the season. In 21 innings pitched between the four clubs, he was 1–1 with a 3.00 ERA. The Reds invited Lorenzen to spring training as a non-roster invitee in 2014. He pitched for Pensacola in 2014, started 24 games, and pitched to a 4–6 win–loss record and a 3.13 ERA in innings pitched. He tried out for the Reds in spring training in 2015 as a relief pitcher, but was reassigned to the minor leagues before the start of the season. He started the 2015 season with the Louisville Bats. The Reds promoted Lorenzen to the major leagues to start on April 29. Lorenzen made his major league debut on April 29, 2015, pitching five innings against the Milwaukee Brewers. He gave up eight hits, including three home runs, walked one and struck out five, and was credited with the 8–3 loss. He stayed with Cincinnati before being optioned to Louisville on August 14. He was recalled by the Reds on August 31. In 27 games for the Reds, he was 4–9 with a 5.40 ERA, and in six starts for Louisville, he was 4–2 with a 1.88 ERA. During spring training in 2016, he was diagnosed with a sprained ulnar collateral ligament in his right elbow, and he did not return until mid-June. He pitched out of the bullpen for Cincinnati upon his return, and he finished the year with a 2–1 record and a 2.88 ERA in 35 relief appearances. In 2017, he was 8–4 with a 4.45 ERA in 70 appearances in relief. Lorenzen was called up to pinch-hit in the seventh inning of a June 30, 2018 game against the Milwaukee Brewers, and hit a grand slam off pitcher Jacob Barnes. It was Lorenzen's third home run of the 2018 season. During the 2018–2019 offseason, Lorenzen worked extensively as an outfielder and stated he had eagerness and desire for the transition to a two-way player and also mentioned interest in spending more time at the plate. On September 4, 2019, Lorenzen became the second player in baseball history to hit a homer, earn the win as the pitcher and play in the field in the same game when the Reds defeated the Phillies, 8–5. The other player to achieve the feat was Babe Ruth on June 13, 1921.
Personal life
Lorenzen is the youngest of four children, all boys, Jonathan, Matthew, and Anthony. Jonathan played professionally and Matthew played college baseball at Cypress and Fullerton Colleges. Both of Lorenzen's parents struggled with drugs and alcohol and frequently fought, with Lorenzen stating that police would show up at his house "almost every single weekend." Lorenzen began experimenting with drugs and alcohol in eighth grade, but stopped when he was 17 after a man read him the Gospel. He is now a devout Christian.
