SAN FRANCISCO -- A milestone night for rookie Abiatal Avelino was sullied by a costly gaffe on the basepaths, one that loomed large in the Giants' 6-4 loss to the D-backs in Monday’s series opener at Oracle Park.

Avelino collected his first career RBI after driving in Kevin Pillar with a single to center field, cutting the deficit to 3-2 in the sixth inning, but he cost the Giants the potential tying run after running through third-base coach Ron Wotus’ stop sign and being nailed at the plate. Avelino attempted to score from second on a one-out single by Brandon Crawford, but he was easily thrown out by D-backs right fielder Jarrod Dyson, undermining the Giants’ rally.

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“That hurt,” manager Bruce Bochy said. “There’s no getting around it. He’s young, and he’s like a wild horse out there. He’s playing hard and he just didn’t see the stop sign. Craw hit it well. He smoked it to the right fielder, one-hopper right to him. Abi actually froze on it, so I just assumed he was not going to go.

“He didn’t break right away, and that’s usually when you know you’re not going to score, especially on a ball hit like that. But he just kept running and knocked us out of a potential big inning there.”

Pinch-hitter Alex Dickerson followed with a walk to load the bases with two outs, but D-backs reliever Matt Andriese struck out Donovan Solano looking to end the inning. Arizona then widened the gap by scoring twice in the seventh and once more in the eighth against San Francisco’s bullpen.

The Giants showed life in the ninth, taking advantage of sloppy defense from the D-backs to score a pair of runs on a sacrifice fly by Evan Longoria and an RBI double by Pillar, but Mike Yastrzemski struck out to end the game, sealing the club’s fifth loss in its last seven games.

Bochy had been looking for a way to get Avelino more at-bats, and with Yastrzemski unavailable to start after being hit by a pitch on the left hand Sunday, the Giants skipper opted to use the 24-year-old infielder in left field Monday for the first time in his career. Despite his limited outfield experience, Avelino held his own in left over the first six innings, though he was removed from the game following his baserunning miscue and replaced by Dickerson in the seventh.

Beede takes step forward

Avelino’s mistake was an act of youthful folly, but on the mound, fellow rookie Tyler Beede showed signs of getting over his own recent growing pains. Beede entered Monday 0-4 with an 8.23 ERA over his last six outings, but he took a step toward climbing out of that rut after holding the D-backs to three runs (one earned) over 5 2/3 innings.

“He should feel good about this outing,” Bochy said. “I thought he had all-around better stuff and command. He looked very composed out there tonight. He was throwing well, and pitching very efficiently, too. It was a good outing for him. We just couldn’t get some runs there. He had us there in the game.”

Beede was one out away from recording his first quality start since July 19, but he couldn’t escape the sixth after a two-out error by Longoria extended the inning. Longoria, a third baseman, was shifted to the right side of second base and couldn’t field a sharply hit grounder off the bat of Eduardo Escobar. Christian Walker and Wilmer Flores followed with back-to-back singles, putting the D-backs ahead, 3-1, and chasing Beede from the game.

Still, the Giants were encouraged by what they saw from Beede, who had been leaving too many balls over the middle of the plate after struggling to repeat his delivery in recent outings. Between starts, Beede worked on refining his mechanics, and his efforts showed in his improved command Monday. He faced 23 batters and threw 18 first-pitch strikes, allowing him to get in more favorable counts and attack hitters throughout the night.

“It’s certainly true that my mechanics haven’t been as sharp as I would want them to be,” Beede said. “I felt much more in control of repeating my delivery tonight, more fluid. I think that allowed my fastball to be a little more sharp and well-located. As long as I continue to feel the way I felt tonight, I think things will be a lot more consistent going forward.”

Gott departs with injury

Right-handed reliever Trevor Gott departed his outing in the seventh inning with right forearm tightness and will undergo tests Tuesday to determine the severity of the injury.

Gott, who celebrated his 27th birthday Monday, struck out Nick Ahmed to lead off the inning, but he then walked Carson Kelly and gave up a single to Tim Locastro. After a flyout from Dyson, Gott issued a second walk to Ketel Marte, leading to a mound visit from a team athletic trainer.

“He was kind of shaking his arm there a little bit,” Bochy said. “That’s why we went out and got him. He felt it a little bit there. It’s not worth the risk. We’ll get some tests done. We’ll know more tomorrow. He didn’t mention one pitch or anything, and his velocity was still pretty good, so that’s always a good sign.”

Gott, who has logged a 4.44 ERA over 52 2/3 innings for the Giants, missed nine games with a right forearm strain earlier this season.