Ireland are continuing to monitor the fitness of fly-half Johnny Sexton in the build-up to Saturday's World Cup Pool A match with Japan in Shizuoka.

Sexton did not train fully on Tuesday but skills coach Richie Murphy said on Tuesday that they expect him to be fit to play against the tournament hosts.

"We expect him to train fully on Thursday," said Murphy.

Murphy revealed that Bundee Aki and Peter O'Mahony have passed their head injury checks and are training fully.

Both players retired hurt during Sunday's comprehensive 27-3 win over Scotland but have successfully come through all three phases of their Head Injury Assessments and are available for selection for the encounter with Japan.

Sexton sustained a minor quadriceps niggle in the victory in Yokohama.

The Ireland skills coach insisted it "wouldn't be unusual" for Sexton to sit out a training session just 48 hours after playing in a Test.

"Johnny went through rehab today, but he had also done some work with the team; but he's being monitored," explained Murphy.

Robbie Henshaw continues to step up the recovery from his hamstring problem that kept him out of the World Cup opener.

Murphy revealed the Leinster centre is back running, and will be reviewed again in the next 48 hours.

While Henshaw is unlikely to be ready to face Japan this weekend, Ireland continue to make positive noises about his recovery.

"Robbie was in training today; he's in his return to play phase now," said Murphy. "He did a lot of running today and came through that no problem.

"We'll see what he's like on Thursday and make a decision on him them."

Keith Earls, Rob Kearney and Joey Carbery are all fit and available for selection for Japan, leaving Henshaw Ireland's only major injury concern - should Sexton recover from his thigh knock.

"Earlsy, Rob Kearney and Joey have all made really good progress, and it's a good situation," added Murphy.

"They were all at the point at the end of last week where they were effectively ready, but we didn't want to take any risks."

Six-day turnaround means 'some rotation'

Ireland can move a long way towards a quarter-final with victory over Japan on Saturday, but Murphy insisted Joe Schmidt's men were taking nothing for granted despite the hosts ranked being just ninth in the world.

Ireland are likely to mix up selection to face the Brave Blossoms, but Murphy insisted changes are not expected to be wholesale.

"The first thing is, we've a lot of respect for Japan. They are a very, very good side and they've proven that over the last couple of years," said Murphy.

"The team we pick will be the team we believe will be the right team to play a Test match six days after the last one.

"There could be some rotation in it but it will be fully focused on beating Japan."