The 33-year-old Kolisi has opted to return to his former Durban-based club Sharks after Racing 92 agreed to terminate his contract. He spent less than one season in France.
A day after the Springboks put a hand on the Rugby Championship trophy by beating New Zealand 18-12 in Cape Town on Saturday, Kolisi - who scored a try in that match and played with a broken nose - told French sports newspaper L'Equipe he felt a bit guilty.
Kolisi arrived in the French league after winning the World Cup a second time with South Africa last year. But he only played 18 matches with Racing.
The flanker explained that he did not know what his international future would be when he signed with Racing.
"Then when I started playing for the national team again, I went to see Racing, we had a chat and they told me: 'It's all good, go and play for your country.' But I realised that for my body...I can't rest," he said.
"And above all, if I play for South Africa, I miss three months of the Top 14 season. I'm very well paid and that makes me feel like I'm stealing from Racing."
Kolisi added another regret.
"I'd like to have won something," said Kolisi, who described the Top 14 as "by far the toughest championship" he has played in.
