Major League Baseball has selected Yankees closer Aroldis Chapman and Brewers fireman Josh Hader as the American and National League Relievers presented by The Hartford of the month for May.

Chapman, 31, went 11-for-11 in save opportunities for the Yankees last month while permitting just one earned run across 11 1/3 innings. The southpaw struck out 18 hitters and walked just three while holding hitters to a .128/.186/.256 slash line as the Yankees surged into first place in the AL East. Chapman’s 11 saves led all relievers in May, and his fastball averaged 98 mph for the month, according to Statcast -- nearly a full mph faster than April.

Hader, 25, racked up six saves for Milwaukee last month while permitting just one earned run over 12 2/3 innings for a microscopic 0.71 ERA. The lefty punched out 21 hitters and walked four, stifling opponents to a .098/.178/195 slash line and one home run as the Brewers climbed into the NL Central lead. Hader has induced 126 misses out of 267 total swings against him for a 47.2 percent whiff rate that is far and away the Majors’ best, according to Statcast. His 57 strikeouts for the season are eight more than any reliever in baseball.