Sinković played multiple sports before transitioning fully to rowing. He first began practicinggymnastics at age three and was briefly a part of the youth setup ofHAVK Mladost, awaterpolo club based inZagreb. He also spent six years playing as afull-back in the youth setups ofNK Zagreb,NK Hrvatski Dragovoljac andNK Lokomotiva football clubs. He began rowing at age 12, together with his brothersMartin and Matija, after their mother signed them up for rowing classes.[8]
In 2017, Sinković married his partner Antonela, a lawyer.[9][10]
Valent first took part in the European championships in theirfourth iteration, held in 2010, with his brothers Martin, as well as with David Šain and Damir Martin in thequadruple sculls category. After the 3/4 of the race was rowed, at 1500 meters, they held the fourth position. Over the course of the next 500 meters, they overtook the German and Ukrainian teams, finishing a second behind the Polish team.[11]
They further took part in the2012 European Rowing Championships as well, likewise competing in the quadruple sculls category. They held the leading position throughout the race, with 2.21 seconds ahead of the second placed team at 1500 meters, and went finished the race 0.92 seconds ahead of the second placed team. The winning time was 6:14.25.[12] Valent was forced to miss part of the 2015 season with a rib injury and the brothers did not compete at the European championships.[6]
Together with his brother, he competed in thedouble sculls category during the2016 European Rowing Championships. They dominated the final race, holding the leading position from the start, with a 2 second lead after 500 meters, and finishing with a 3.68 second lead. Their winning time was 6:56.52.[13]
In the2018 European Rowing Championships, Valent competed with his brother Martin in thecoxless pair category. They were second best for the first three quarters of the race, before taking over in the last 500 meters and finishing first, with a time of 6:26.42.[14] The two brothers continued competing in the coxless pair in the2019 European Rowing Championships as well, holding the leading position throughout the race, and finishing first with a time of 6:22.46.[15] He and his brother competed in the coxless pair once again during the2020 European Rowing Championships, finishing in the second place, behind the Romanian Tudosa/Cozmiuc pair.[16]
Together with David Šain, Damir Martin and his brother, he participated in the2012 Summer Olympics inLondon, in thequadruple sculls event. The team had no issue qualifying to the final race, coming into it as favorites. However, the German representatives would hold almost a boat lengths lead in the final race, with the Croatian team just barely winning the silver medal, as the Australians finished close behind.[17]
He would change disciplines for the2016 Summer Olympics inRio, competing in thedouble sculls event together with his brother. In the final race of the event, the brothers held a narrow lead over the Lithuanian representatives, who overtook them by the 1500 meter mark. They would in turn overtake the Lithuanian team in the final 500 meters of the race, finishing the race first with a time of 6:50.28,[18] 1.11 seconds ahead of the second placed team.[19] Following this victory, theWorld Rowing Federation would award them the "Team of the Year" award.[20]
Sinković competed in the2020 Summer Olympics inTokyo, entering thecoxless pair event with his brother Valent. The pair entered the final race as overwhelming favorites to win the gold medal, with a betting coefficient of 1,03 and won with a time of 6:15.29.[21] The Sinković brothers competed in the2024 Summer Olympics inParis in thecoxless pair event. The pair trailed the other teams for a majority of the final race before overtaking the British leading team during the final 200 metres to win with a time of 6:23.66.[22][23]
His first appearance in the world championships came at the2010 World Rowing Championships, when he competed in the quadruple sculls. The Croatian team won the gold medal, finishing with a time of 6:15.78, 1.26 seconds ahead of the second placed team.[24] In the2011 World Rowing Championships, he won the sole bronze medal of his career, failing to defend his gold medal from the previous year.[25] The same team competed in the2013 World Rowing Championships, in the same category, finishing with a time of 5:53.57 and winning the gold medal.[26]
During the2014 World Rowing Championships, he switched to the double sculls, competing together with his brother. They broke the world record in the qualifying race, managing to cover the distance of 2 kilometers in under six minutes (5:59.72). In the final race, they finished first.[27] They competed in the same category in the2015 World Rowing Championships, once again winning the gold medal.[28]
In the2017 World Rowing Championships, he competed in the coxless pair for the first time in his career, once again with his brother. The pair finished in the second place, winning the silver medal.[29] The two of them competed in the same category in the2018 World Rowing Championships. They won the gold medal, finishing with a time of 6:14.96, 1.94 seconds ahead of the second placed team.[30] They defended their gold medal at the2019 World Rowing Championships, finishing with a time of 6:42.28.[31]
Valent and his brother Martin Sinković competed in the double sculls event of the 2022World Rowing Championships. They placed fourth in the A final, finishing five seconds behind the winning French crew.[32] They stayed in the double scull for the2023 World Championships in Belgrade and finished with a silver medal in the A final, earning a 2nd placing in the world rankings and qualifying that boat class for Croatia for the2024 Paris Olympics.
