Published Jul 21, 2018 at 10:22 AM | Updated at 1:20 PM PDT on Jul 21, 2018
San Francisco is home to "the biggest rugby party in the world" for a weekend as 40 teams from 28 different countries on six continents compete in the The Rugby World Cup Sevens at AT&T Park.
Even if you don't understand rugby, photos clearly illustrate how hard rugby players work. And it shows in their faces.
Check out some of the best photos from the tournament: