Adam Duvall's two-run single was all Cincinnati needed as the Reds beat the St. Louis Cardinals 2-1 on Wednesday night.
The Reds' third win in their last four games dealt a blow to the Cardinals' playoff hopes. St. Louis remained one game behind San Francisco for the NL's second wild card, with the New York Mets 1 1/2 games ahead of the Giants.
Iglesias earned his fifth save in six opportunities with two innings of relief, pitching in and out of jams in both.
Cardinals pinch-hitter Kolten Wong led off the ninth with a triple. But Iglesias got a shallow fly sandwiched between two ground outs to end the game.
Reds starter Anthony DeSclafani (9-5) allowed one runner in each of the first four innings, but only once during that span did the Cardinals have anyone in scoring position. He stranded five runners, including two in the sixth, his last inning. He allowed six hits and one run.
Cardinals starter Mike Leake (9-12) allowed five hits and two runs in five innings, striking out six.
Leake was lifted for pinch-hitter Matt Adams in the fifth and he grounded into a double play that scored Aledmys Diaz for the Cardinals' lone run.
Cardinals manager Mike Matheny brought closer Seung Hwan Oh in with one out in the eighth inning. Oh struck out both batters to get the Cardinals out of a jam after Duvall tripled to lead off the inning.
Oh left the game with two outs in the ninth after being hit by a line drive from Jose Peraza.
Alex Reyes (4-1, 1.58 ERA) has earned a win in his last three appearances. He is 0-0 with a 2.57 ERA in three career appearances against Cincinnati.