Andrei Arlovski
Sergei signed a deal to fight for Strikeforce and made his debut on February 12, 2011. He faced former UFC Heavyweight champion Andrei Arlovski in the opening round of Strikeforce 2011 Heavyweight Grand-Prix. Sergei defeated Andrei Arlovski by knockout in the first round. Sergei faced Josh Barnett, who defeated Brett Rogers on June 18, 2011 at , in the next round. He lost via submission in the first round.