Racing PositionsMets' Alvarez returns; Senga's rehab paused5MMets put struggling Polanco on IL with sore wrist7MThree young arms are here to carry the Mets into October1YJorge CastilloMets send Senga to Triple-A: 'Right thing to do'1YCatcher Alvarez rejoining Mets from minors1YMets demote struggling catcher Alvarez to minors1Y