Nishikori, Sock advance, Brooksby upsets Anderson on first day of Citi Open

With the summer hard court season in full swing, the Citi Open Washington kicked off with Kei Nishikori booking his spot in the second round on Monday.

The 2015 champion defeated Sam Querrey 6-4 6-4 to secure his spot in the next round, improving to 7-4 in career meetings against the American. After having just competed at the Tokyo Olympic Games where he reached the quarterfinals, the World No.67 showed little sign of fatigue as he needed just 86 minutes to secure the victory.

In a Hall of Fame Open final rematch, #NextGenATP star Jenson Brooksby avenged his loss to former World No.5 Kevin Anderson. The young American required an hour and 50 minutes to secure a 7-6(4) 6-3 win over the South African. Fellow American Jack Sock booked his spot in the second round, earning a walkover victory over Yoshihito Nishioka 6-7(3) 4-0 after the Japanese star was forced to retire in the second set.

Canadian veteran Vasek Pospisil rallied from a set down to escape with a 4-6 6-3 6-3 victory over Ecuadorian qualifier Emilio Gomez. Italian journeyman Andreas Seppi battled past Japan's Yasutaka Uchiyama in a 3-6 7-5 6-3 encounter. The 37-year old advanced to the next round along with Belarusian Ilya Ivashka, who defeated compatriot Egor Gerasimov 7-5 6-4 earlier in the day.