In the 2005–06 Russian Superleague (RSL) regular season, Mozyakin had a tight scoring race with Aleksey Morozov and Evgeni Malkin for the top scorer of the league.

In the 2007–08 RSL regular season, which would be its final in existence before being absorbed into the KHL, Mozyakin had another tight scoring race with Morozov and finished the season only one point ahead of Morozov, leading the league in goals (37) and points (64).

[1] In the 2013–14 KHL season, he won the Gagarin Cup with Metallurg Magnitogorsk as team captain and leading scorer.

Mozyakin has also been a regular member of the Russian national team, taking part in all twelve EHT games in the 2007–08 season.

Sergei and his wife Yulia have a son, Andrei, and two daughters, Maria and Daria.