Black reportedly is on waivers. If he goes unclaimed, the deal can be completed now. If he is claimed, he will need to be pulled back and be sent to the Mets after the season.
Black, 25, was the 49th overall pick in the 2009 draft out of Dallas Baptist University.
He appeared in three games at the major league level this season. Black is 5-3 with a 2.51 ERA and had 17 saves in 38 relief appearances with Triple-A Indianapolis this season. He has an upper-90s mph fastball and slider.
The Mets already have acquired second baseman Dilson Herrera, who has been assigned to low-A Savannah.