Tokyo (AFP) – Tennis star Naomi Osaka admis she has gone through “more down than up” in her career this year, as she tries to break out of a slump at The Pan Pacific Open in Tokyo this week. In a season hampered by injury, the former world number one and four-time Grand Slam champion has plummeted to 48 in the women’s tennis world rankings after a run that has seen her crash out in the first round of her last three tournaments.