Kevin Connolly BLASTS Robinson Cano -- IS HE SMOKING CRACK?

Robinson Cano must've been high on crack when he demanded the Yankees pay him $300 million … ‘cause he’s wayyy overrated and a lazy base runner … this according to "Entourage" star Kevin Connolly.

Connolly – a huge Yankees fan – vented about Cano and his agent (Jay Z) asking for the record setting contract today on Twitter … and suggested the Yanks send their former 2nd baseman packing.

Cano -- now a free agent -- is holding out for a 10-year $310 million contract … and he could be headed to the Mets if the Yankees don't pay up.