Sinitsyn started for the Moscow sports organization Dynamo in Yekaterinburg. He made his international debut on December 7, 1997 in the B-World Cup , where he celebrated his first victory in Gällivare, Sweden . A few weeks later he made his World Cup debut with a seventh place in Oberwiesenthal . In February 1988 Sinizyn took part in the Olympic Winter Games in Nagano and finished in the Gundersen individual competition with more than two minutes behind the Norwegian Bjarte Engen Vik a good tenth place. He finished the season in 16th place in the overall World Cup.
In the 1998/99 season Sinitsyn achieved his greatest successes and was tenth in the overall World Cup. After he narrowly missed the podium twice with fourth place in the individual competitions in Lillehammer and Schonach , he took third place at the Nordic World Ski Championships in Ramsau in 1999 and thus won the bronze medal. In the team competition on the large hill followed by 4 × 5 km cross-country skiing, he was able to win bronze again.
After he missed the points in the 1999/00 World Cup season , Sinizyn again competed in the second-rate B World Cup. Even there, however, he could no longer achieve any podium positions, which is why he ended his career in 2002.