Orioles from AAA Norfolk on June 7, 2017. Jackson was designated for assignment on June 11 and elected free agency two days later. Return to Washington (2017–2018) On June 16, 2017, Jackson signed a minor-league contract with the Nationals, making this his second stint with the franchise. After several outings with the Class-AAA Syracuse Chiefs, allowing just one earned run in innings of work, Jackson was promoted to the Nationals' major league roster to take injured starter Joe Ross' rotation spot for a July 18 start against the Los Angeles Angels of Anaheim. Jackson earned the 4–3 win, spinning seven innings of three-hit ball and allowing his only runs on solo home runs by Mike Trout and Martín Maldonado, and manager Dusty Baker said he would continue starting for Washington. He resigned a minor-league contract on January 11, 2018. He was assigned to AAA Syracuse Chiefs for the 2018 season. On June 1, 2018, the Nationals released Jackson from his minor-league contract after he opted out. Oakland Athletics (2018) Jackson signed a minor-league contract with the Oakland Athletics on June 6, 2018, and was assigned to the AAA Nashville Sounds. He was called up to start for the Athletics on June 25, tying a Major League record of having played for thirteen different teams. Jackson earned his 100th career victory on July 30, 2018, in a 10–1 win over the Blue Jays. Toronto Blue Jays (2019) On May 11, 2019, Jackson was traded to the Toronto Blue Jays in exchange for cash considerations. On May 15, 2019, Jackson made a start against the San Francisco Giants, becoming the first player ever to play for 14 different teams in MLB. Jackson posted an 11.12 ERA through eight games (five starts). On July 16, 2019, he was designated for assignment. On July 20, 2019, Jackson was released. Return to Detroit Tigers (2019) On July 22, 2019, Jackson signed a minor-league contract with the Detroit Tigers and assigned him to the Triple-A Toledo Mud Hens. In two starts for the Mud Hens, Jackson allowed five earned runs on 11 hits in innings, two strikeouts and four walks. On August 9, the Tigers selected Jackson's contract from the Mud Hens and promoted him to the majors. Jackson recorded an 8.47 ERA in 10 appearances with the team. Jackson became a free agent following the 2019 season. Return to Arizona Diamondbacks (2020) On February 2,