Casper Ruud suffers shock loss to qualifier Marcos Giron at Japan Open
World number eight Ruud, who reached this year's French Open final, lost in the Beijing Open quarter-finals before bowing out in the last 16 of the Shanghai Masters this month.
Ruud's Asian swing ended with a 6-3, 6-4 defeat to American world number 79 Giron in Tokyo, but he tried to stay positive, noting his fall at the first hurdle at last year's tournament.
"I think it went better than last year so what can you say, I played better than last year, for sure," said the tournament's number two seed.
"Maybe not what I was really hoping for and kind of what I needed but there's still a couple of weeks to go and I'll keep my head high and try to fight in the last couple of weeks of the year."
Ruud had to work hard to beat Japan's Yosuke Watanuki in a 7-6 (8/6), 6-3 first-round win on Tuesday night.
He said he was "never able to get into a rhythm" against Giron in a match that lasted just 1hr 20min.
"I tried to play the same level as I did yesterday - maybe I wasn't able to but it's OK, it's not always easy to shift from one day to the other with different opponents," said Ruud.
"I wasn't able to be ready enough for his game and counter his game."
German number three seed Alexander Zverev and American Frances Tiafoe, seeded sixth, had already been eliminated in the first round in Tokyo.
Shanghai Masters champion Hubert Hurkacz joined them after losing to China's Zhang Zhizhen.
Zhang, who won gold at the Asian Games in the Chinese city of Hangzhou last month, beat the Pole 3-6, 6-4, 7-6 (7/4).
American number five seed Tommy Paul booked his place in the quarter-finals alongside Canada's Felix Auger-Aliassime, the number eight seed.
Paul beat fellow American Mackenzie McDonald 6-4, 6-2 to progress in his tournament debut.
Paul said the "very fast" Tokyo court was to his liking.
"The fast ones are a little bit more fun because you can really take advantage of well-struck shots and get to the net," said the 26-year-old.
"It's quicker points, your serve is a little bit more effective. I do enjoy a fast hard court."
Auger-Aliassime beat Austria's Sebastian Ofner 6-4, 6-1.
