The many reasons David Cone is endorsing J.A. Happ

J.A. Happ’s Yankees debut couldn’t have gone much better Sunday. The 35-year-old lefty brought in from Toronto to stabilize their rotation shut down the Royals — and even though cellar-dwelling Kansas City is far from the toughest test, David Cone believes Happ is ready for whatever he faces in his new home. Cone has experience with…