MIAMI -- From the first inning, there were signs it could be a long night for Marlins rookie Jordan Yamamoto. Although the 23-year-old retired the side in order, he allowed three hard-hit balls.

The outing slipped away from Yamamoto in the fourth inning, as he surrendered a grand slam to Nick Ahmed that helped launch the D-backs to a 9-2 win over the Marlins on Saturday at Marlins Park.

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“First time through, they were very aggressive, swinging at everything,” said Yamamoto, who made his eighth career start. “Second time through [the order], they were very patient, just waiting for that one fastball. And they didn't miss it. Even the offspeed, they were waiting for the offspeeds I threw up, curveballs, especially, and they were hitting it.”

The loss snapped Miami’s three-game winning streak.

Miguel Rojas belted a leadoff homer for Miami, but that lead was erased in Arizona’s six-run fourth.

For Yamamoto (4-2, 3.64 ERA), it was the second straight loss. Walks and home runs caught up to him in both games.

At the Dodgers last Sunday, the rookie was tagged for two homers and walked two in four innings. On Saturday, in the fourth inning, he hit a wild stretch, and Ahmed did the big damage with the grand slam.

“It's just bad execution, but along with that, the conviction,” Yamamoto said. “Not having the conviction to throw it. Not being in the right mindset, not being focused. It's just one of those times, I guess, you have to be better.”

The Marlins anticipate some bumps in the road for Yamamoto, who got the promotion to the big leagues from Double-A Jacksonville and made his MLB debut on June 12.

“Base on balls,” Marlins manager Don Mattingly said. “It's been a bit of an issue, and it's something he's going to have to get a hold of.

“As things were going good, no one was talking about base on balls, and things like that. When you start looking at a long-term view, it's hard to sustain success when you're putting people out there too often.”

Yamamoto’s growing pains are another reminder that even though the Marlins have a talented, young starting staff, collectively, it is not a finished product.

That’s why trading any of their controllable starters is considered risky.

Caleb Smith and Trevor Richards, who was just moved to the bullpen, have attracted interest on the trade market.

Miami on Saturday also made a deal postgame, sending closer Sergio Romo, Minor League pitcher Chris Vallimont and a player to be named later to the Twins for first-base prospect Lewin Diaz.

“We won’t stop looking at opportunities to improve the organization,” Marlins president of baseball operations Michael Hill said. “We’ll continue to work the phones and talk to our peers and see if there are opportunities to get better.”

Yamamoto is trying to make his mark to show he belongs in the rotation.

And the game featured a benches-clearing incident in the eighth inning when Tayron Guerrero plunked Christian Walker with a 98.6 mph fastball. It was the second time Walker was pegged in the game.

But the big damage came in the fourth inning. Yamamoto had retired the first nine he faced, but the rookie walked Jarrod Dyson to open the fourth. Ketel Marte walked, and Eduardo Escobar delivered an RBI single.

Yamamoto hit Walker with a 91.7 mph fastball, and two batters later, Ahmed blasted his grand slam.

“They came out, they started taking pitches, and being less aggressive,” Yamamoto said. “Walk, walk. Hit by pitch. Home run.”

But even though Yamamoto didn’t allow a baserunner until the fourth inning, Dyson opened the game with a fly ball that Brian Anderson caught on the warning track in right field. Marte followed with a grounder that had an exit velocity of 103.5 mph that struck the side of Yamamoto’s right foot, but the ball deflected to third baseman Martin Prado for the second out. And the inning ended on Escobar’s liner, which was was snared by first baseman Garrett Cooper, who made a leaping catch. The expected batting average, per Statcast, was .950.

Yamamoto’s fastball velocity was down from his previous start, last Sunday at the Dodgers. On Saturday, his four-seam average was 90.9 mph, with a maximum speed of 92.4 mph. At Los Angeles, his average was 92.3 mph, and he topped at 95.3 mph.

“It got to the point where I tried to do too much with the pitches,” Yamamoto said. “I tried to be too perfect with the pitches. I tried to put the pitches in there, rather than just throw it.”