Birutis started his professional career when he signed with BC Žalgiris-2 in summer 2014. On January 5, 2016, in a match against BC Petrochema he made a National Basketball League record by rebounding 23 balls. Later, that season he won silver medals with Žalgiris-2, who lost the final game against BC Sūduva. On 14 April 2017, after dominating in the second-tier National Basketball League with 17.4 points, 9.0 rebounds, 1.4 assists and 2 blocks averages per game, Birutis was invited to join the top-tier Lithuanian Basketball League playoffs team Vytautas Prienai–Birštonas. Birutis powerfully debuted on 15 April 2017 by scoring 17 points and grabbing 4 rebounds, but his team lost 92–89 after Justas Tamulis buzzer-beater. Two days later, he achieved his first 96–89 victory in LKL versus the Neptūnas Klaipėda, and he was second-best Vytautas' scorer with 19 points and 6 rebounds.
On 1 August 2017, Birutis joined his hometown team BC Šiauliai. During the 2018 Karaliaus Mindaugo taurė quarter-final versus the Lithuanian champions Žalgiris Kaunas, Birutis played his career-best game by scoring 35 points, grabbing 11 rebounds, dishing out 2 assists and blocking one shot, however his team lost 85–78. On 18 April 2018, Birutis entered his name into the 2018 NBA Draft. During his second LKL season, he led all three main statistical lines of his position in the league: 14,9 points, 7,3 rebounds and 1,3 blocks. After his astonishing season, Birutis has received the LKL Most Valuable Player Award. Moreover, with his help BC Šiauliai recovered from having the worst record in the league last season and became a solid playoffs participant by finishing in the 5th place during the regular season. During the season closing ceremony he was also named as the best young player of LKL. It was announced at the end of the season that Birutis would return to Žalgiris for the 2018–2019 season.
Birutis joined Lithuanian champions BC Žalgiris and had debut in EuroLeague on 12 October 2018 against Saski Baskonia. He scored 7 points in 10 minits. Birutis struggled all season from start with injury, couldn't practise because of pain, which leaded to surgery on 14 February 2019. On 1 June he won his first Lietuvos krepšinio lyga title.
BC Prienai
On 23 November he came back after recovery from injury, and had 9 points and 4 rebounds including game-winning shot in 16 mins in a thrilling win 81:79 against BC Pieno žvaigždės. Later he earned player of the month award in February. He had his best game on 1 February 2020 against BC Neptūnas in which he scored 25 points and gathered 36 efficiency value. In that season he averaged 15,2 points, 7 rebounds and 20,4 efficiency.
Monbus Obradoiro
On July 24, 2020, he has signed with Monbus Obradoiro of the Spanish Liga ACB.
