NEW YORK — Mets supplemental-round Draft pick Anthony Kay underwent Tommy John surgery on Tuesday to replace a damaged ligament in his left elbow, the Mets announced, joining fellow left-hander Steven Matz on the operating table. Kay will miss the entire 2017 season. The Mets’ second selection in the 2016 Draft, Kay, 21, starred at UConn with a 2.64 ERA over three seasons. But he signed with the Mets for only $1.1 million, $872,000 under Major League Baseball’s slot recommendation for the 31st overall pick. That was due to concern over a physical exam that raised issues regarding Kay’s elbow, according to MLB.com’s Jim Callis.