SAN FRANCISCO -- Jae-Gyun Hwang's first major-league home run was not accompanied by his trademark bat-flip Wednesday afternoon.

Maybe next time, he insisted.

"I don't plan it (beforehand)," the Korean standout explained after his first major league hit, a solo home run in the sixth inning, proved to be the difference-maker as the San Francisco Giants completed a three-game sweep of the Colorado Rockies with a 5-3 victory.

Left-hander Ty Blach overcame his own defensive miscues to take a lead into the seventh inning, and the San Francisco bullpen took it from there to finish off the club's first three-game sweep of the season and the first of the Rockies since 2013.

"This game's about picking each other up," Blach insisted. "That's what we did in this series. Everybody contributed. That was an awesome win for us."

The loss was Colorado's eighth in a row. The Rockies had begun the series with a 10-1 record against the Giants this season.

"If our record in the second half of the season is just like the first half, we'll take it," Rockies manager Bud Black insisted of his 47-34 club. "In the present, it's rough. It's rough sledding right now. But the big body of work has been solid."

Promoted from Triple-A Sacramento earlier in the day after having played the past 10 seasons in his native South Korea, Hwang belted a 2-0 pitch from Rockies rookie left-hander Kyle Freeland well into the left field bleachers to snap a 3-3 tie.

The 29-year-old, who accumulated 115 home runs in 1,184 games abroad before hitting seven in 68 games at Triple-A this season, became the 17th Giant since 1919 to hit a home run for his first hit in his major league debut. Adam Duvall had been the last to do so in 2014.

"The only thing I imagined was setting my feet on the field here at AT&T Park," he said of his expectations in his debut. "I never imagined hitting a home run.

"I've had some great moments (in my career). Hitting a home run in my first (Major League Baseball) game ... it's unreal."

The Giants celebrated both in the dugout after the go-ahead homer and in the clubhouse after the win.

"It's a special moment," Giants manager Bruce Bochy said. "You have tough times in this game. But there are special moments you try to savor."

Nick Hundley had a two-run homer in a three-run fourth inning, helping the Giants rally from an early 2-0 hole.

Hundley's third homer of the season came after Freeland had dropped Hwang's one-hopper back to the mound, preventing a potential inning-ending double play and allowing the Giants' first run to score.

Hwang was awarded with his first RBI on the play.

The Rockies tied the score in the sixth with the help of Blach's second throwing error of the game. This one, on a bunt single by Pat Valaika, went into the right field corner, allowing the Colorado second baseman to reach third base.

He scored when Mike Tauchman, who had been promoted from Triple-A Albuquerque on Tuesday, lined a single to center field for his first career hit and RBI.

Blach was pulled with one on and one out in the seventh. Right-hander George Kontos, lefty Steven Okert and righty Hunter Strickland retired eight of the nine batters they faced in the final 2 2/3 innings.

Strickland posted his first save of the season.

The Giants gave their bullpen an insurance run after Gorkys Hernandez scored on Brandon Belt's fielder's choice grounder in the eighth to increase the San Francisco lead to 5-3.

Blach (5-5) allowed seven hits and three runs (one earned) in 6 1/3 innings. He walked three and struck out six.

"He hurt himself," Bochy noted afterward. "His command was worse throwing to first base than anywhere."

Freeland (8-6) gave up four runs and seven hits in six innings. He walked one and struck out two.

The Rockies scored two runs in the top of the first after Belt, the Giants' first baseman, couldn't handle Blach's wide throw on Charlie Blackmon's game-opening dribbler.

Nolan Arenado put Colorado up 2-0 when he plated Blackmon and Ian Desmond with a two-run single.

"If we continue to play the way we're playing, we're not going to be anywhere we want to be," Arenado said. "The Giants, (Los Angeles) Dodgers and (Arizona) Diamondbacks, the way we've played against them (in the past week and a half), they know we're better than that."

Hwang had two RBIs and Hundley two hits for the Giants, who hadn't won three in a row since May 14-16.

Desmond and Arenado collected two hits apiece for the Rockies, who out-hit the Giants 8-7.

Colorado is now 0-6 on its nine-game trip.

NOTES: Both teams reached the midpoint of the season. The Rockies (47-34) are 10 games ahead of where they were last season; the Giants (30-51) are 20 games behind last year's pace. ... Giants closer RHP Mark Melancon (straight right pronator) had a PRP injection in his right forearm. He and 3B Conor Gillaspie (back spasms) were placed on the 10-day disabled list, creating roster spots for 3B Jae-Gyun Hwang and RHP Dan Slania, who was promoted from Double-A Richmond. ... Both teams are off Thursday. The Rockies complete a nine-game trip with a three-game series beginning Friday at Arizona. The Giants open six-game trip Friday at Pittsburgh. ... The Giants have scheduled LHP Madison Bumgarner (separated left shoulder) for an injury-rehab start Friday night at Triple-A Sacramento.