TOKYO (AP) Defending champion Kei Nishikori, of Japan, was given a real scare by teen ace Borna Coric, of Croatia, on Monday, before sealing a 2-6, 6-1, 6-2 comeback win in the first round of the Rakuten Japan Open.
The 38th-ranked Coric, the youngest player in the top 50 of the ATP world rankings, showed a maturity beyond his years to take the first set, and looked likely to upset the home-crowd favorite.
However, the 18-year-old won only one of the next nine games as the sixth-seeded Nishikori eventually advanced to the second round in in two hours and eight minutes.
''In the first set I played too good, out of my limits, and in the second I just couldn't maintain the level,'' said Coric, who spearheaded Croatia's Davis Cup victory over Brazil last month.
''I'm still very young. I can see that I've so many things to work on for maybe two or three years. I need to improve for sure.''
Nishikori is seeking his third triumph in this event, which he also won in 2012, and his fourth title of the season, having tasted success in Memphis, Washington and Barcelona.
''I was hitting too short in the first set, and I was rushing a little bit. I had a lot of unforced errors,'' said Nishikori, whose only competitive appearance since his first-round exit at the U.S. Open in late August had been in Japan's Davis Cup defeat of Colombia.
''In the second set I started playing more patient, and at the same time stepping up and being more aggressive. Third set I was playing great.''
He next faces the big-serving Sam Querrey, of the U.S., who defeated the 35th-ranked Alexandr Dolgopolov, of Ukraine, 7-6 (7-5), 6-4.
The 50th-ranked Querrey, routinely breaking 210 km/h (130 mph) on his first serve, achieved the only break in the ninth game of the second set, before serving out for the match.
The 127th-ranked Tatsuma Ito won the battle of the Japanese wild cards against the 148th-ranked Yoshihito Nishioka, 3-6, 6-0, 7-5.
Ito's second-round opponent will be either top-seeded Stan Wawrinka, of Switzerland -- who he beat in the first round last year -- or the veteran 121st-ranked Radek Stepanek, of the Czech Republic.
Wawrinka told journalists the ankle injury that forced him to retire from an event in Metz, France, last month, was no longer a concern.
''It was a week without playing tennis, but yesterday I practiced for two hours and I think I'm 100 percent and ready for the tournament,'' said the fourth-ranked Wawrinka.
He faces the 36-year-old Stepanek on Tuesday.
Monday's final match saw the 40th-ranked Jiri Vesely, of the Czech Republic, dismiss wildcard Yasutaka Uchiyama, of Japan, 6-4, 6-4.