Abbott was recalled from Triple-A Rochester on Friday.
Abbott was claimed off waivers by the Giants in early May and will join the major-league bullpen after spending the last month and a half with the Triple-A club. He made six appearances (two starts) in Rochester and posted a 9.00 ERA and 2.00 WHIP in 13 innings. The right-hander should be deployed as a multi-inning reliever by the Nationals.