U.S. tennis roundup: who's in and who's out after Day 1 in Tokyo

Six Americans competed on the first day of tennis competition at the Tokyo Olympic Games -- four in singles and two in doubles. Results for the U.S., whose singles entrants are all Olympic debutants, were mixed. 

Tommy Paul, the only American male singles player who qualified outright for the team, lost to Russian Aslan Karatzev, 3-6, 2-6 in 75 minutes. Tennys Sandren was also knocked out of the singles contest, but put up a battle in his first set. He fell 5-7, 2-6 to Spain's Pablo Carreno Busta.

Jessica Pegula dropped her match to Switzerland's Belinda Bencic in two sets, falling 3-6, 3-6. Alison Riske, too, was bounced from the Olympic singles competition, but put up a fight through three sets. She fell 7-5, 6-7, 4-6 to Romania's Mihaela Buzarnescu.

The sole American winners on day one were Frances Tiafoe and Rajeev Ram, one of two U.S. men's doubles teams. The duo took out the No. 6-seeded Russian team of Karen Khachanov and Andrey Rublev 6-7, 7-6, and 12-10 in a tiebreak. Ram won a silver medal at the 2016 Games alongside Venus Williams in mixed doubles. 

Tiafoe faces Kwon Soon-Woo in singles on day two. The U.S. will also see Marcos Giron and remaining women's singles team member Jennifer Brady each play, as well as the Nicole Melichar/Alison Riske and Austin Krajicek/Tennys Sandgren doubles teams.