SAN FRANCISCO -- Brandon Crawford had Buster Posey's back Friday night, even if Patrick Corbin's fastball barely didn't.

Crawford responded to a pitch thrown behind his All-Star teammate and his manager's corresponding ejection with a two-run home run that sparked a comeback as the San Francisco Giants defeated the Arizona Diamondbacks 6-2 in the opener of a three-game series.

The loss came while the Diamondbacks were finalizing a trade with the Boston Red Sox in which Arizona dealt closer Brad Ziegler for right-handed pitcher Jose Almonte and infielder Luis Alejandro Basabe.

"It's hard. He's been so good for us in that role and he's been a good Diamondback for a long time," Diamondbacks manager Chip Hale said of Ziegler. "It's just something that has to happen. We should have played better and these things wouldn't be happening."

Both managers -- Hale and the Giants' Bruce Bochy -- were ejected by home plate umpire Quinn Wolcott in separate incidents during San Francisco's first home win of the season over Arizona in five tries.

The home team won for just the second time in 12 meetings between the Giants and Diamondbacks this season.

Right-hander Jeff Samardzija overcame a first-pitch home run by Diamondbacks second baseman Jean Segura to win for just the second time since May 24.

"The guys responded for me," Samardzija praised. "It was cool to see everyone get fired up."

The leadoff home run was Segura's third of the season, the second as the first batter of the game.

One inning later, Samardzija was involved in the dispute that ended Bochy's night.

The first-year Giant hit Segura in the left elbow in his first plate appearance after the home run. Arizona led 2-0 at the time.

"We're in the business to win ballgames," Bochy responded when asked if Samardzija was sending some kind of message to Segura. "We're not trying to hit guys."

When Corbin, the Diamondbacks' starter, first threw near Posey's knees and then behind him another foot or two higher, Wolcott had seen enough and issued warning to both benches.

Bochy objected to his warning and was tossed, his first ejection of the season.

"I can't have Buster being a target," he explained. "I'd had enough of it."

After Posey walked, Crawford blasted the fourth pitch he saw over the right-field wall for a tying home run, his ninth of the season.

"I really wanted to make them pay," Crawford insisted. "I wanted to get him in. Fortunately, I got us both in."

Clearly, Crawford got more joy from this home run that most others.

"Given the situation, it felt really good," he assured. "For regular season, it ranks right up there."

The Giants took the lead for good when they scored twice in the third, including once on Crawford's third RBI, which came on a two-out single after an error by Arizona third baseman Jake Lamb had extended the inning.

A bases-loaded walk by second baseman Grant Green in the fifth added to San Francisco's lead and ended the night for Corbin (4-7).

Samardzija (9-5) retained the 5-2 lead into the seventh before turning the game over to the Giants' bullpen. He allowed two runs and five hits in 6 1/3 innings, walking three and striking out six.

"You have to regroup," he said of the second first-pitch home run he's allowed this season. "Tough way to start the game. But I like the way it finished."

Samardzija helped his own cause with a leadoff double in the two-run third. He eventually scored on Lamb's error.

Three Giants relievers combined to blank the Diamondbacks on two hits, getting four of the eight outs on strikeouts.

Gregor Blanco's pinch-hit home run leading off the bottom of the eighth, his first of the season, completed the scoring.

It was the first pinch-homer of Blanco's career.

Crawford had three of the Giants' eight hits, complementing his homer and single with a double. He finished with three RBIs, giving him a team-best 58 for the season.

Posey scored twice and Brandon Belt walked a career-high four times for the Giants (55-33), who became the first team in the majors to win 55 games.

The come-from-behind win was the Giants' 28th of the season, surpassing last year's total of 27.

Paul Goldschmidt had two hits and Yasmany Tomas drove in the second run of the first inning with a single for the Diamondbacks, who had won 10 or their previous 11 at AT&T Park.

Corbin's second-to-last pitch led to Hale's ejection.

Leading 4-2, the Giants loaded the bases with one out in the bottom of the fifth before Corbin got Mac Williamson to hit into a fielder's choice, with Belt being thrown out at the plate.

Corbin then came within one out of escaping the jam, but Wolcott wouldn't give him a called strike on a 2-2 curveball to Green.

Corbin walked Green on the next pitch and was pulled in favor of right-hander Jake Barrett, with Hale getting thrown out for barking at Wolcott about the 2-2 pitch on his way to the mound.

"I felt like at that point Patrick had earned it," Hale explained. "It's probably not the right thing to do, but at that point I was frustrated and wanted to show Patrick. I felt like it was a strike, but you know, the umpire's got the final say."

The ejection was Hale's third of the season.

Corbin was charged with five runs (three earned) in his 4 2/3 innings. He allowed five hits and five walks, and struck out one.

NOTES: Diamondbacks manager Chip Hale said the club will reinstate RHP Daniel Hudson from the bereavement list on Saturday to fill the roster spot left open by the RHP Brad Ziegler trade. ... The ejections were the 69th of Giants manager Bruce Bochy's career and the fifth of Hale's career. ... Giants SS Brandon Crawford has 52 RBIs since May 1, third-most in the majors behind DH Edwin Encarnacion of the Toronto Blue Jays and OF Adam Duvall of the Cincinnati Reds. ... San Francisco 1B Brandon Belt won the Final Vote among the fans for the National League's last All-Star spot. This marks Belt's first career All-Star appearance. Arizona 3B Jake Lamb finished fourth among the five players in the NL's Final Vote. ... San Francisco RHP Matt Cain (strained right hamstring) threw 5 2/3 innings in an injury-rehab start at Triple-A Sacramento on Friday night. He is scheduled to make another minor league start next week before being considered for reinstatement from the disabled list, Bochy said.