PBF's last prime fight was against JMM after that fight there has been a gradual decline his defense was not as good nor was footspeed or his hand speed. His countering also declined especially the pull counter. Let the haters tell you that PBF is the only fighter who has been prime his whole career.
Last prime fight for me was the Hatton fight. Layoff after that bout, and you can see a very slow, but gradual decline fight to fight after that. Just my opinion.