Ruzavin began to make an impact at senior level in 2006, placing fourth at the Russian Race Walking Championships. His first senior call-up came at the 2007 European Race Walking Cup, where he ranked 34th overall. At the 2008 national championships he competed over the novel 35 km distance and managed third place in a race won by world record holder Vladimir Kanaykin. Stepping up in distance, he entered the 50 kilometres race walk for the 2008 IAAF World Race Walking Cup, but did not perform well and failed to finish the competition. His performances over 20 km began to improve at the 2009 European Race Walking Cup, where he ranked 19th. He also edged up in the national rankings, coming second to Andrey Krivov in the 20 km event. He received his first senior medal at the 2009 Universiade, forming a Russian 1–2 with champion Sergey Bakulin. A senior title came at the end-of-season IAAF Race Walking Challenge Final, where he was victorious over the shorter 10 km distance ahead of both Stanislav Emelyanov and Eder Sánchez. He came 38th at the 2010 IAAF World Race Walking Cup20 km race. In 2010 he ranked within the top four nationally at both the winter and summer championships and repeated that feat the year after. He was less successful at international level, failing to finish the 50 km distance at the 2011 European Race Walking Cup and managing only 17th in the 20 km race at the 2011 Universiade. Working under coach Viktor Chegin, his form turned around in the 2012 season as he opened with a personal best of 1:17:45 hours to win the 20 km title at the Russian Winter Walking Championships. He was beaten by training mate Sergey Morozov at the summer championships. He gave his best performance of his career at that point at the 2012 IAAF World Race Walking Cup, finishing in fifth after Morozov's subsequent disqualification.
Global competition and medal
At the 2013 Russian winter championships Ruzavin was second to Pyotr Trofimov, but gained selection for the 2013 European Race Walking Cup and shared in the team title with winner Denis Strelkov and Aleksandr Ivanov. He was the winner at the summer Russian championships ahead of stable-mate Petr Bogatyrev in a time of 1:19:08 hours. He led from the start at the 2013 Universiade, held in Kazan, but fell back to fourth place while fellow Russian Andrey Krivov won the title. Ruzavin gained selection for the 2013 World Championships in Athletics hosted by Moscow – his first major global championships – but despite being among the favoured entrants he could not match his earlier form and was well down the field in 49th place, nearly twelve minutes behind gold medallist Aleksandr Ivanov. Ruzavin raised himself into fifth on the all-time rankings for the infrequently held 5000 m indoor walk, recording a time of 18:15.54 minutes at the Samara Cup. A fourth-place finish at the Russian Winter Walking Championships earned him another international selection for the 2014 IAAF World Race Walking Cup and had his second fastest 20 km finishing time at the point with 1:18:59 hours – this brought him the bronze medal, although poor performances by his compatriots meant he did not secure a team medal. Ruzavin was suspended from competition by RUSADA in October 2014 due to abnormalities in his biological passport. His suspension marked a continuation of a series of doping bans emerging from Viktor Chegin's Mordovia walking school, the most prominent being Olympic champion and world record breaker Elena Lashmanova.
