Manager’s Mets cap flap ap

THE cover for Marty Appel’s book “Casey Stengel: Baseball’s Greatest Character” shows the Old Perfessor’s wrinkled face under a baseball cap offering a big wink — but is it a Yankees cap or a Mets cap?

Stengel (inset) managed the Yankees to seven World Series championships before he be- came the first manager of the Mets, who he said “have shown me more ways to lose than I even knew existed.” Doubleday, which is publishing the book Tuesday, justt in time for Opening Day, cropped the cover photo so Yankee fans won’t know it’st’s a Mets cap.