Claressa Shields advances at World Boxing Championships

This time, Claressa Shields had to work for a victory.

The American middleweight and Olympic gold medalist won a four-round decision over Lidia Fidura of Poland on Thursday to advance to the quarterfinals at the women’s World Boxing Championships in Jeju, South Korea.

Shields had won her first bout of the tournament against Hellen Baleke of Uganda in all of 11 seconds, just long enough to throw a few punches before Baleke’s corner threw in the towel.

Thursday’s victory might have set up a quarterfinal rematch with England’s Savannah Marshall — the only woman to defeat Shields in an otherwise unblemished career — but Marshall lost her bout against Russia’s Iavoslava Iakushina.

Featherweight Tiara Brown, a U.S. boxer and a reigning world champion, won Thursday. Teammates Alex Love and Destiny Chearino lost close decisions.