Kei Nishikori was unwilling to use excuses for his loss to Marin Cilic at the ATP World Tour Finals on Friday.

The Japanese star entered the clash in London knowing his place in the last four was secured, after Andy Murray beat Stan Wawrinka earlier in the day.

While Nishikori suffered a 3-6 6-2 6-3 defeat to Cilic, he insisted his focus was on his meeting with the Croatian.

"I wasn't thinking too much [about Saturday]," he said.

"I was just trying to focus on the match. Unfortunately, it was a tough loss but hopefully I can play better [in the semi-finals]."

Nishikori faces world number two Novak Djokovic in the last four, having suffered nine straight losses to the Serbian.

But the fifth seed believes his form is good enough to claim a win, saying: "I'll try to think tonight or tomorrow about what I have to do to beat Djokovic.

"Obviously I'm not playing bad so we'll see tomorrow, maybe."