Japan's Kei Nishikori upended top seed Marin Cilic to reach the semifinals at the $1.212 million U.S. National Indoor Tennis Championships.

The fifth-seeded world No. 22 Nishikori knocked out the 12th-ranked Cilic in 6-4, 6-2 fashion at The Racquet Club of Memphis.

Cilic titled in Zagreb in his native Croatia just two weeks ago and had an eight-match win streak snapped.

Nishikori will next face Australian Marinko Matosevic, who outlasted No. 7 seed Alexandr Dolgopolov of Ukraine, 6-7 (6-8), 6-2, 6-4 in a little over two hours.

Friday's last two matches assured no American would advance to the final, as Jack Sock and Michael Russell each fell in straight sets.

Feliciano Lopez of Spain, who advanced to the quarterfinals with a walkover win over three-time Memphis champion Tommy Haas, downed Sock, 6-4, 6-3, while Uzbekistan's Denis Istomin ousted Russell, 6-4, 7-6 (7-5).

The 2013 Memphis champ will claim $291,800.