Josh Hader has not given up a run in five appearances this season, totaling 7.2 Innings pitched. All five of those appearances counted as saves for the Milwaukee Brewers, and he has tallied 13 strikeouts along with just one walk and one hit given up.
The fact that he has five saves shows how Hader has had to step into a new role, because even in his dominance last season, he was not typically the closer. If he were to close games, it would be him being brought in the 7th or 8th inning and just finishing the game, which is what happened Sunday against the Cubs when he went 2.