I stumbled across this: Hardball And Kingman. Excerpts below from a long entertaining piece you should check out.
I readily admit that I am disturbingly fascinated by Dave Kingman—more fascinated than anyone should be about a man who famously sent a live rat to a reporter. Mostly it comes down to my theory: I think Kingman could have been a great player only he did not particularly want to be a great player.
My main proof for this is the 1979 baseball season. Kingman was playing for the Chicago Cubs that year. And I had always heard that in the months before that season, Kingman decided he finally would show everyone just how great he could be if he actually tried. Up to that point, Kingman had been one of the most absurd players in baseball history—he hit a lot of home runs, and he struck out an obscene number of times, and he got hurt a lot, and he only played defense in the loosest definition of the word, and he was traded and waived three times in the same year (and released at the end of that year). He also seemed to have a unique ability to make everybody really despise him.
in New York, the much-publicized Dave Kingman character came out—here was the moody Kingman who swung hard at everything, who almost never walked, who pulled everything, who hit 500-foot home runs and 325-foot pop-ups, who ran the bases like a child coming in for dinner, who played defense not just poorly but with utter disdain. He did mash 36 and 37 home runs his two full years with the Mets, and Shea was a terrible hitters park. Those home runs seemed to be the only things that intrigued him at all about baseball. The Mets traded him in ‘77, the Padres waived him, the Angels traded him and the Yankees let him go.*