CHICAGO — J.T. Realmuto took a step in front of home plate and waited for the throw, while the Wrigley Field crowd held its breath as the night’s outcome seemed to be riding with the baseball coming in from right field.

The Phillies traded for Realmuto three months before their 5-4 win over the Cubs on Monday night. And when they did, they proclaimed him to be the best catcher in baseball. Their belief stemmed not only from Realmuto’s work at the plate, but also what he provides behind it.

Monday night, he showed them what he can do when he’s in front of it, too.

Realmuto made a game-saving tag in the bottom of the fifth, plated the tying run in the top of the sixth, scored the final run of a three-run rally, and then came through once more with a go-ahead homer in the 10th.

The Phillies won their fourth straight game, Jake Arrieta held his own in his return to Chicago, and a challenging seven-game road trip started with an emphatic win that felt so unlikely so many times during the night.

“Probably what stands out about J.T. even more than one play is the well-roundedness,” manager Gabe Kapler said. “It’s the at-bats. It’s the leadership. It’s the preparation, the game-calling, the tags, the throws. We talked about us acquiring the best all-around catcher in the game and it’s hard for me to imagine there’s a better one out there.”

Realmuto’s 10th-inning homer came two innings after Seranthony Dominguez washed away that three-run rally by allowing three runs in the eighth. It came an inning after Andrew McCutchen, down to the team’s last strike, laid off four straight pitches to extend the ninth with a walk and allow Jean Segura to drive in the tying run.

“That walk by McCutchen doesn’t get talked about enough,” Realmuto said. “That was a huge walk to keep the inning alive.”

But none of that likely would have been possible had it not been for Realmuto’s play in the fifth.

He positioned himself as Bryce Harper uncorked a strong yet slightly off-line throw from right field in the fifth inning. Harper had just caught the second out of the inning and Cubs third-base coach Brian Butterfield sent Anthony Rizzo charging for home.

“I really thought I threw that ball into the third deck to tell you the truth,” Harper said. “I just tried to rear back and throw it as hard as I could to the plate.”

Realmuto stepped ahead of the plate, grabbed the throw, and made an athletic sweeping tag. The inning ended with the double play.

“Honestly, when he threw the ball, all I was thinking in my head was ‘Just catch it. Don’t mess this up. Catch this and put the tag on.’ He made a great throw and I was able to get the tag down,” Realmuto said. “It was a huge play for the game.”

The Cubs seemed to be a hit away from putting the Phillies away after loading the bases with an out. Instead, their threat ended without a run and the Phillies’ rally was ready to begin.

The Phillies scored three two-out runs in the top of the sixth. Realmuto reached low for a two-strike, game-tying single off Yu Darvish, who had stymied the Phillies up to that point. Cesar Hernandez followed with a two-run triple to the right-field corner.

The Phillies not only had a rally, they had a lead. They seemed to ride the momentum from Harper and Realmuto’s inning-ending double play.

“Maybe the biggest play of the game,” Arrieta said. “But it’s tough to say. Just a really good ballgame between two really good teams.”

The lead did not last as Dominguez was pushed back out for the eighth after needing just 11 pitches in the seventh to retire Kyle Schwarber, Kris Bryant, and Anthony Rizzo. That second inning was too much. The first two batters reached on walks and Kapler elected to stay with Dominguez despite having Pat Neshek warmed up in the bullpen.

With Dominguez limping, Daniel Descalso cracked a liner to left-center field that fell between Andrew McCutchen and Odubel Herrera. Two runs scored to the tie game and then Descalso was awarded home for the go-ahead run when Segura’s relay throw smacked him in the leg.

“We have to do a better job communicating,” McCutchen said. “I’ve got to catch that ball. It’s a ball I know I can catch. We’re still learning each other. Once he knows I can get that ball, he doesn’t have to go 100 percent to get it. Those balls can’t hit the ground.”

McCutchen recovered with his two-out walk and Segura atoned for his misfired throw by knocking in the tying run. An inning later, Realmuto would again come through.

“Not only what J.T. does behind the plate, but his ability to have incredible at-bats and what he did tonight with the go-ahead homer, just speaks volumes for his character, his work ethic and the type of teammate he is,” Arrieta said.

Arrieta pitched one more inning after Harper and Realmuto connected for the double play. It was his best inning of the night. He needed just nine pitches to retire the three batters he faced in the bottom of the sixth to provide the perfect shutdown inning the Phillies needed. He allowed one run on eight hits with four strikeouts and two walks. Arrieta did not have his best stuff, but he limited the damage and kept the Phillies close.

And his biggest asset was Realmuto, who made sure Harper’s throw was good enough for the final out of the fifth and kept the Phillies within striking distance. When the Phillies traded for Realmuto, they said it was a move that could move the needle. He moved the needle at Wrigley Field for the biggest win of the season.

Get insights on the Phillies delivered straight to your inbox with Extra Innings, our newsletter for Phillies fans by Matt Breen, Bob Brookover and Scott Lauber. Click here to sign up.