Now that Davis Cup awards ranking points you can't exclude his win. Every year is different. Just because he had a great South American run two years ago doesn't mean it's always his strongest part of the season. In fact traditionally it was one of his weaker months.
Losing to Mayer and Nishikori is nothing compared to losses he's had in the European clay swing to much lower ranked players. The only real suspicion here is that he's 32 years old when critics always question motivation. Every losing streak is hyped ten fold because of age.
He just looks done to me..... think this will be his last year on tour, he doesn't have the physical ability to do his talents justice anymore.