Leimanis started his career with
Ventspils, with which he made his first professional career in the
Baltic League. During his first two seasons, his playing time was not big, but he managed to win with Ventspils the
Baltic League in
2013 and the
Latvian League in 2014. The following two years, he played with
Liepājas Lauvas. At his second year, in 62 matches at the Latvian and Baltic League, he averaged 8.4 points and 3.9 assists in 23.2 minutes per game. In the 2016–17 season, he returned to
Ventspils, making his debut also in the
Basketball Champions League. Overall in 41 games in the year in all competitions, Leimanis averaged 4.4 points and 1.3 assists in 12 minutes per game. At the start of the 2017–18 season, he joined
Liepājas Lauvas for a second stint. After making really good appearances with the team, he finished the season with
Valga-Valka of the
Latvian–Estonian Basketball League. On July 17, 2018, he joined
Koroivos of the
Greek 2nd Division. On July 4, 2019, he joined
Ciudad de Valladolid of the LEB Oro (Spanish 2nd Division). On July 14, 2020, Leimanis signed with
Tsmoki-Minsk of the
VTB United League. After a year in Minsk, Leimanis signed with
BC Odesa in Ukraine. Playing for Odesa he averaged 13.5 points on 41% shooting from three point distance. After the season was cut short in Ukraine, Leimanis signed with
Neptunas in Lithuania to finish the season there. In August 2022, he joined
CB Estudiantes. ==Latvian National Team==