U.S. Open finalist Kei Nishikori and Canadian star Milos Raonic are the only seeded players left that are still in contention for the crown at the Rakuten Japan Open Tennis Championships in Tokyo on Thursday.

The fourth seeded Nishikori overpowered Donald Young of the United States 6-4 6(6)-7(7) to advance to the quarterfinals.

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The 24-year-old Japanese will next face Jeremy Chardy of France who defeated seventh seeded Kevin Anderson 6-4 6-4.

Third seeded Raonic had a relatively easy match against Austrian Jurgen Melzer 6-4 6-3 to make his way into the quarters against Denis Istomin who won over Polish qualifier Michal Przysiezny 6-4 7(7)-6(5).

Nishikori is sixth in the list of players that are in contention of being part of the year-ending WTA World Tour Finals to be held in London this coming November.

Wolrd No. 1 Novak Djokovic, Roger Federer and Rafael Nadal have already qualified. Nishikori is almost assured of being part of the elite group and will become the first ever Asian player to compete in the event.

Raonic on the other hand is in ninth place behind David Ferrer, who was eliminated early in the tournament, and Tomas Berdych who is currently playing at the China Open.

If both Raonic and Berdych proceed to the finals, Ferrer will drop to ninth or possibly even 10^th place if Andy Murray performs well in Beijing.

In other matches, Benjamin Becker disposed of Japan's Tatsuma Ito in straight sets 6-3 6-3 to setup a quarters matchup against American Jack Sock who defeated Andrey Golubev in three sets 6-3 1-6 7-5.

Frenchman Gilles Simon had to come back from behind after dropping the first set against Gilles Muller 4-6 7(7)-6(1) 6-3 and faces Steve Johnson of the United States in the quarterfinals after defeating Marcel Granollers of Spain 4-6 6-3 6-4.

TagsKei Nishikori, Milos Raonic, David Ferrer, Tomas Berdych