Struggling grand champion Kisenosato withdrew from his fifth consecutive tournament on Friday, a day after suffering a demoralizing fourth defeat at the ongoing New Year Grand Sumo Tournament.

Although he pulled out citing injury, with just one tournament of perfect attendance in six meets at sumo's highest rank, the 31-year-old has all but guaranteed he will be forced to make a decision on whether to retire from the sport.

According to his stablemaster Tagonoura, Kisenosato aggravated an existing injury to the left side of his chest in his loss to second-ranked maegashira Yoshikaze on the fifth day of the 15-day tournament.

"I'm sure he wanted to compete, but we can't make his injury worse," Tagonoura said. "We want to start off by focusing on his treatment and build up his body."

The hugely popular Japanese grand champion had been making his return to the raised ring at Ryogoku Kokugikan after a year slowed by the chest injury, in addition to problems with his left upper arm, left ankle and lower back. His third consecutive loss on Thursday left him with a 1-4 record for the meet.

His withdrawal leaves Kakuryu as the only remaining yokozuna in the tournament after fellow Mongolian Hakuho injured his left big toe in his loss Wednesday to Yoshikaze and pulled out the following day. The all-time record holder for sumo championships departed the tournament with a 2-3 record after forfeiting Thursday's bout.

Kakuryu, who entered Day 6 with a 5-0 record, said the absence of the other grand champions would not affect his approach to the tournament.

"I haven't given it any thought. I just want to concentrate on my own sumo one day at a time," the Izutsu stable wrestler said. "Although I may gradually tire from here, it's important to take care with my preparations."

The 32-year-old has a better understanding than most of the situation Kisenosato faces, having likewise pulled out of the past four tournaments due to an injured right ankle.

"Making the decision to retire from a tournament is painful," he said.

If historical precedent is an indication, the chances of Kisenosato successfully returning to the sport are relatively slim.

Another injury-plagued grand champion, Musashimaru, announced his retirement from sumo mid-tournament in 2003 after dropping out of the six preceding meets.