Once the Mets offseason plan became clear and through spring training, a key question they faced was how to handle first base. The early returns have been perhaps worse than anyone could have imagined.  Jorge Polanco, signed to a two-year, $40 million contract with the hopes that he could transition from the middle of the infield to first base, has been hurt most of the season and played poorly when on the field. Brett Baty, introduced to the position during spring training, has been inconsistent in the field and at the plate . He’s shown flashes of his lefty power, but also entered Wednesday in an 0-for-10 skid. And then there’s Mark Vientos, who has struggled badly on both sides of the ball, looking to recapture at least the power he displayed two years ago, which seems to be more and more of a distant memory. Mets third baseman Mark Vientos (27) falls off the bag, allowing a batter on during the ninth inning when the New York Mets played the Minnesota Twins on Wednesday, April 22, 2026.…