When Jorge Lopez threw a pitch too close for comfort to Andrew McCutchen’s head, the Pittsburgh Pirates icon held his bat in one hand and pointed at the Washington Nationals reliever.

As tempers flared and benches cleared Wednesday night, Oneil Cruz played the peacemaker by stepping between McCutchen and Lopez as heated words were exchanged.

After McCutchen drew a walk to load the bases, Cruz delivered a devastating blow by crushing a grand slam to right field that sent the crowd of 8,529 at PNC Park into a frenzy in a five-run inning that boosted the Pirates to a 6-1 win.

“I don’t know if he got fired up. I think our whole club, as you can see, got fired up,” Pirates manager Derek Shelton said. “They took a little bit of offense to what happened, and because of it, it ended up sparking a big inning.”

Those fireworks overshadowed a strong start by Pirates left-hander Bailey Falter (1-2), who entered the game with a 7.20 ERA and coming off a five-walk performance in a 5-3 loss to the Cincinnati Reds. Falter tossed a two-hit shutout over seven innings.

“Honestly, just thinking back on my last one,” Falter said. “I had a lot of time to reflect on that, told myself I was going to do everything possible to not let that happen again.”

Falter was efficient in throwing 57 of his 83 pitches for strikes, recording two strikeouts against one walk, while facing the minimum number of batters (21) through seven. He allowed a first-inning single to James Wood, who was caught stealing on a throw by catcher Henry Davis to second base. Nathaniel Lowe singled to start the fifth, and Luis Garcia Jr. drew a full-count walk in the sixth but Falter followed by getting groundouts for double plays.

“He came right out and attacked their lineup,” Shelton said. “I thought he was outstanding. That was about as good as we’ve seen him.”

Nationals starter Mitchell Parker (2-1) struck out the first four batters he faced. The newest addition to the Pirates finally got a hit with two outs in the second inning, as Jared Triolo was activated from the 10-day injured list and singled to left. Isiah Kiner-Falefa followed with a single to center, and Enmanuel Valdez drew a walk to load the bases. But Parker got Henry Davis to fly out to center field to escape.

Where Davis missed on a chance at a grand slam in his first plate appearance, he got his first home run of the season in his next at-bat. With one out in the fifth, he blasted Parker’s 1-0 elevated fastball 392 feet and off the left-field foul pole to give the Pirates a 1-0 lead.

“I was glad I kept it fair,” Davis said of his first homer since a solo shot June 12 at St. Louis. “Little bit of relief for sure. I knew it was hooking. I was just really glad to see it hit the foul pole.”

A Pirates baserunning gaffe led to an unusual outcome in the sixth. Cruz was on first when Tommy Pham hit a fly ball to left field. Cruz started toward second but thought the ball was caught by Wood, so he spun around and headed back to first base. Wood threw to first, and Pham was tagged out in a play that was scored a 7-3 putout.

“There is nothing you can do,” Shelton said, crediting first base coach Tarrik Brock for holding Cruz at first. “T. Brock actually did a good job keeping him there, and the umpires did a really good job because it was kind of a convoluted play and they got it right.”

The Pirates padded their lead in the seventh against Lopez, when Kiner-Falefa hit a leadoff single to left, raced to third on a single to right by Valdez and scored on Davis’ broken-bat groundout to third for a 2-0 lead.

After Lopez hit Bryan Reynolds with a pitch, he threw a wild pitch near McCutchen’s head that allowed both runners to advance into scoring position. The close call came the day after Pirates starter Mitch Keller hit Paul DeJong in the face with a pitch that forced the Nationals third baseman to not only leave the game but be placed on the 10-day injured list.

“It was way too close to his head,” Shelton said. “Bryan had gotten hit two pitches before. And then we go above Cutch’s head? Not a fan of that. And I think the umpires did a really good job of controlling it, knowing the situation. I mean, if this stems from something from (Tuesday), Mitch did not try to hit Paul DeJong in the face in a 1-0 game. It was totally accidental. If this was retribution for that, then that’s just lack of awareness.”

Both benches cleared when McCutchen and Lopez exchanged words, with McCutchen holding his bat and pointing at Lopez before Cruz stepped in.

“You clearly see everybody’s got each other’s backs,” Davis said. “We’re playing for each other. You love the guys in the clubhouse. You love coming to the field everyday knowing that we all got each other’s backs, especially when it’s Cutch out there. It’s good to see.”

There’s a history between Lopez and the Pirates, as he served up a tying three-run homer to Reynolds and the go-ahead solo shot to McCutchen while with the Chicago Cubs last Sept. 2 in a 5-3 comeback win. Home plate umpire Ron Kulpa ejected Lopez, and Eduardo Salazar walked McCutchen to load the bases.

“Every game is different, and every situation is different,” Shelton said. “So if we’re stemming that from a game last year in August, we’ve got to be better than that.”

Cruz then drilled Salazar’s first pitch, a slider low and inside, for a 385-foot line drive to right field for a grand slam and 6-0 lead.

After Caleb Ferguson tossed a scoreless eighth, the Nationals prevented the Pirates from getting their first shutout win of the season against Chase Shugart in the ninth. Dylan Crews hit a leadoff single, advanced on Luis Garcia Jr.’s walk and a Nasim Nunez groundout and scored on a sacrifice fly by Alex Call.

Shelton was quick to note that Cruz’s slam separated the game.

“That’s what it’s all about,” McCutchen said. “You don’t want to ever have to get to that point, but it’s good for us to show up as a team and keep the game going, not let the moment get to high or heighten off the moment, running off the emotion and letting your emotion take over. Then you try to do something you’re not supposed to be doing.

“But Cruz showed up. Lit a fire under him. He was able to hit a grand slam. Sometimes it’s needed. We ended up being on the good end of it.”