rtokens: " Each time he fights , he 's on the last frontier of his career .
pos: CC DT JJ TO DT NN VBP IN DT NN WP VBZ VBN NNS IN CD JJ NN NNS : JJ , VBN , JJ NN CC NN : VBZ VBG JJ TO DT NN IN PRP$ NN .
tokens: But those close to the boxer acknowledge that the man who has won championships in four different weight classes -- lightweight , welterweight , junior middleweight and middleweight -- is drawing close to the end of his career .
ltokens: I 'm not retiring , " Duran told Reuters .