"Brian is working very hard and over the last two or three days he has put in some good rehab work," said Kiss.
"The medical staff are doing a fantastic job with him.
"Talking to him today after the session he was very happy where he ended up.
"He has another rehab session tomorrow and a couple of days rest where he will obviously be doing a little bit of stuff and we will see how he goes after that."
The 31-year-old is with the Ireland team at their camp in Limerick and the squad will move to Dublin next week ahead of the Springbok match.
The Ireland squad are still based at their Limerick camp but will move to Dublin at the start of next week.
Keith Earls (ankle) is still a major doubt for the opening game and the Munster back again sat out of training yesterday, but Kiss is in confident mood after their first week together.
"We've all been waiting to get together in preparation for a fairly tough schedule and the Springboks game first up has really been our focus," he added.
"I have to complement the guys.
"They've come here and embraced the new ideas that the coaching staff have put on the table and they have added their own bits to the mix and we're grateful they have put in such a good performance this week."