Olympic gold medalist John Shuster remained undefeated through his first three matches at the USA Curling National Championships on Sunday at Kalamazoo, Mich.

After beating Chase Sinnett 8-1 in the morning round, Shuster beat Scott Dunham's rink 9-5 in the afternoon to improve to 3-0 in round-robin action at Wings Event Center. Defending national champion Rich Ruohonen is also 3-0 after winning 8-3 over the Mark Fenner rink that contains Duluth's Korey Dropkin.

Duluthian Cory Christensen opened with an 8-4 victory over skip Annmarie Dubberstein before playing a late match Sunday.