The Mets are planning to fill a vacancy in their starting rotation with one of the game’s top prospects, handing right-hander Noah Syndergaard his Major League debut on Tuesday against the Cubs at Wrigley Field. Right-hander Dillon Gee is expected to be placed on the 15-day disabled list with groin pain, clearing a spot for Syndergaard, considered the Mets’ No. 1 prospect and the No. 11 prospect in baseball, according to MLB.com.