Poor decisions on the bases cost the Cubs in a 5-4 loss Friday to the Reds at Wrigley Field.

After Seiya Suzuki doubled to left field in the ninth inning, third-base coach Willie Harris sent baserunner Nick Madrigal home with what would have been the tying run. But Reds shortstop Elly De La Cruz was the relay man and threw a 93.3 mph rocket to catcher Tyler Stephenson to nab Madrigal at the plate.

Harris, who always has an aggressive mindset, sensed an opportunity to tie the score, but the play backfired. Instead of having runners on second and third with one out and Cody Bellinger at the plate, it was just Suzuki on third with two outs. Bellinger flied out to end the game.

It was a questionable call when you factor in that Madrigal ranks in the 58th percentile for sprint speed, according to Baseball Savant.

‘‘Willie has been fantastic, and his aggressiveness has got us a lot of runs this year,’’ said manager Craig Counsell, who was ejected for the second time this season while protesting whether a pitch hit Madrigal during his at-bat in the ninth. ‘‘It didn’t work this time.’’

Harris said he felt confident sending Madrigal because of left fielder Jacob Hurtubise’s arm strength. Plus, with Bellinger coming up, he figured the Reds would walk him to load the bases had he held Madrigal at third.

‘‘I’m trying to score right there,’’ Harris said. ‘‘It didn’t work out for us, unfortunately. But you have to be aggressive. You have to try to score runs.’’

Harris also took accountability for Dansby Swanson’s baserunning gaffe in the fourth. With two outs, Pete Crow-Armstrong singled on a grounder to second baseman Jonathan India, who made a diving stop and threw to third base. Swanson, who had started the play at second, came too far around third and was tagged out to end the inning.

‘‘Coming around third, if that ball scoots through to center field or [India] bobbles it a little bit, we’re safe at home, but he made a play,’’ Harris said. ‘‘It’s the big leagues. They make plays sometimes, and sometimes it doesn’t work out for us. Today, it was one of those days where it didn’t work out for me particularly.’’

It was a frustrating May for the Cubs, who finished the month 10-18. Their margin for error is small, especially when they’re making mistakes on the bases.

There’s not much the Cubs are doing right at the moment. Their bullpen gave up three runs, their defense is ranked 25th in the majors in runs saved (minus-13) and their offense is scoring below the big-league average.

But the miscues on the bases are inexcusable because they’re one aspect of the game the team and players can control. Entering the game, the Cubs had made the second-most outs on the bases in the majors (25).

‘‘With Willie, we’ve sent runners aggressively, and that’s gotten us runs,’’ said Counsell, whose team continued to struggle with runners in scoring position (2-for-12). ‘‘The play at third with Dansby, that’s a tricky play. Now, there’s been some others throughout the season that we made some mistakes.’’

It’s one thing to lose, but it’s another to beat yourself. Whether because of their bullpen, their sluggish offense or their miscues on the bases, the Cubs continue to give away games within their grasp.

‘‘Moving forward, I’ll be less aggressive with one out, knowing the situation a little bit better,’’ Harris said. ‘‘But today it’s on me. I know those guys in the clubhouse; they know me, and they know I’m for them. They’ll pick me up tomorrow.’’