Ireland head coach Joe Schmidt allayed injury concerns over Johnny Sexton following the team's opening World Cup win over Scotland.
The 34-year-old out-half twice received treatment to his leg in the opening half and declined goal-kicking duties following Tadhg Furlong's 25th-minute try.
The Leinster back was replaced by Jack Carty with 22 minutes to play of the 27-3 success.
"He was able to kick, that was us being super-cautious because we got such a good start," Schmidt told RTÉ Sport after the match.
"We felt we could cover him up a little bit and we got him and Conor [Murray] off reasonably early.
"We thought they were really big for us in the pivot area with their kicking game and just their game sense, they controlled things really well for us in that first half.
"[They] got us through the first 15 minutes of the second half and then I felt that we were probably far enough in front close enough to that last quarter that we could bring them off and get them ready for a six-day turnaround, which is going to be tight with Japan having an eight-day turnaround."
Ireland lost flanker Peter O'Mahony and Bundee Aki following Head Injury Assessments in the first half and Schmidt said they must wait and see how they fare over the next while.
"They are both fine now, which is reassuring but we'll have to wait and they have to go through the protocols of HIA 2 and HIA 3 to determine whether or not they have suffered a concussion," added the New Zealander.
"For us, six days is the minimum to turn around after a concussion so we’ll just see how they are symptomatically but right here, right now, there is a bit of reassurance around those two.
"Potentially [there is a problem at centre], less so Pete because we’ve got Rhys [Ruddock] to come back in to the mix.
"At centre, Chris, he opened them up a few times, he was very big in the air, he’s there, and Garry Ringrose, and Keith Earls has played there in the past and so has Jordan Larmour so we can mix and match a little bit."
While Ireland's forwards scored three of the four tries, the Kiwi was eager to spread the praise.
"The [pack] were super but I thought there were some good performances from Jordan Larmour, Jacob Stockdale, Garry Ringrose, their defence was outstanding,
"Andrew Conway finished his try well but in the first half, Tadhg's try, CJ taking off fromthe back of the scrum, James Ryan getting over, the strength of those guys and how well they teamed up, that whole collective pack effort was outstanding and it gave us a foothold in the match."