The 32-year-old netted three goals and provided two assists in 16 appearances in 2013/14.
"I can sum up the season as the kind of season that makes one to look forward to the next season," Nkosi told his club's official website.
"I am busy analysing the information from my performances and working out a plan to do better next season.
"My season was interrupted by the injuries despite making some contribution to the team when I was called up to play.
"I am not happy with my contribution during the past season. I have my back against the wall now. I will not rest during this off-season period. I cannot rest, I have to work hard to prepare for a better upcoming season," concluded the former Arminia Bielefeld attacker.