ATLANTA -- For three innings on Friday night, everything was going smoothly for Pablo Lopez. The 23-year-old was in command, keeping his pitch count down, while running up his fastball to 96.7 mph.

Things began to change in the fourth inning, when Lopez engaged in a full-count tussle with Ronald Acuña Jr. On the sixth pitch, Acuna drove a down-and-away changeup over the right-field wall for an opposite-field, two-run home run.

The Braves never looked back, rolling to a 4-0 win over the Marlins in the series opener at SunTrust Park.

“Everything is going to be a learning experience,” Marlins manager Don Mattingly said. “He wasn't as aggressive that whole [fourth] inning.”

Lopez was tagged for four runs in a 36-pitch fourth inning, getting beaten twice by the long ball. Along with Acuna, Tyler Flowers hit a solo shot to left as nine came to the plate.

“I'd say the main thing was the breaking ball wasn't there like it was in the first three innings,” Lopez said. “I wasn't getting on top of it. I didn't have the right spin. It didn't have the consistency. You can't expect the results when you're missing spots like that and they're putting good swings on it.”

The turning point in the inning was the Lopez and Acuna showdown. Venezuelan countrymen, Lopez started Acuna off with a fastball away, called a ball. Lopez then got a called strike with a two-seam (or sinking) fastball, and then mixed in a curveball, again taken for a ball away.

Acuna fouled off a changeup, and then took a curveball away to run the count full. After delivering three straight offspeed pitches down in the zone, Lopez threw a changeup down and away, and Acuna blasted it over the right-field wall.

“I could have been out of the at-bat a little quicker if I executed some balls up in the zone better,” Lopez said. “He worked the count 3-2 and got the pitch he was looking for, and he hit it with the barrel.”

The full-count changeup actually matched strength against strength. Opponents last year batted .125 against Lopez’s change. But Acuna, the reigning National League Rookie of the Year Award winner, mashes changeups.

Entering Friday, since the start of 2018, Acuna led MLB (min. 25 results) with a .412 (14-for-34) batting average against the pitch, and ranked third with a .853 slugging percentage. In that span, only Mike Trout (.978) and Nelson Cruz (.918) had a higher slugging percentage.

"Every at-bat I’m usually looking for a fastball,” Acuna said. “But he threw a changeup. So, I let it come in a little further and I was able to make good contact."

The way Kevin Gausman was cruising through the Marlins’ lineup, the Braves right-hander didn’t need much support. After JT Riddle's second-inning single, Miami went without a hit until Brian Anderson singled in the seventh, and finished with three hits on the night.

Lopez made it through five innings, giving up the four runs on seven hits with five strikeouts. In four of those frames, the right-hander threw 15 or fewer pitches. Even in the fifth inning, he recovered for three quick outs on 14 pitches, including catching Acuna looking for his final strikeout.

“I was able to realize the things I wasn't doing in the fourth inning, and come back in the fifth [with] a little more aggressiveness,” Lopez said. “I was getting after it and trusting more of my fastball instead of getting away from it, and just helped the bullpen with one more inning. That was a big thing.”

Dialing up to 100

The Tayron Guerrero of old returned on Friday night. In a scoreless eighth inning, according to Statcast, the hard-throwing right-hander had his four-seam fastball top 100 mph 11 times, including one stretch of seven straight. His maximum speed was 101.7 mph.

“I feel I’ve been building it up,” Guerrero said. “The first few games I’ve felt good, but it wasn’t like today. Today was more like the adrenaline was kicking in. That’s why.”

Of 18 four-seamers thrown, his average on the pitch was 99.8 mph.

Entering Friday, Guerrero had touched 100 mph just once this year, and his season average velocity was 97.5 mph.

Guerrero said he worked with pitching coach Mel Stottlemyre Jr. on getting more balance and drive from his back leg.

“I was working with the the pitching coach today,” he said. “Use more of your legs. Get more balance with my back leg and let it go. I felt it was better the first pitch I threw to Acuna. This is what I was doing last year.”