SAN FRANCISCO -- Rookie Antonio Senzatela overcame a rocky start for his second straight victory on a rainy afternoon, and the Colorado Rockies won a four-game series in San Francisco for the first time in club history.
Senzatela settled down after a rough first inning, holding San Francisco scoreless on four hits over the next six innings in the Rockies' 4-3 victory Sunday.
"We jumped out to the quick lead, we ambushed their guy, and then they jumped on Antonio," Colorado manager Bud Black said. "A lot of young guys would have let it get to them."
Senzatela (2-0) allowed three runs on seven hits in seven innings overall. Mike Dunn struck out the two batters he faced in the eighth, Adam Ottavino got another out and Greg Holland pitched a perfect ninth for his seventh straight save this season.
Each team scored three times in the first inning.
Though rain fell throughout the first five innings and resumed briefly in the eighth, San Francisco avoided its first home rainout in more than a decade. The last time rain forced cancellation of a game at AT&T Park was in April 2006.
"It was a little difficult, but you need to find a way to lock in in these conditions," Arenado said. "You have to figure out how to be comfortable when you're uncomfortable."
Blackmon hit the game's third pitch into the right-center stands, extending his club record with his 23rd career first-inning leadoff homer. Colorado began with four straight hits off Jeff Samardzija, capped by Arenado's double.
Samardzija (0-3) struck out eight while allowing four runs in seven innings.
"The balls were in the middle of the plate, especially in the first inning," Samardzija said. "Not to have good stuff out there today was frustrating, and to start out that way makes the rest of the day a lot tougher."
DJ LeMahieu had a run-scoring single for Colorado in the second.
The Giants traded minor league RHP Clayton Blackburn to the Texas Rangers for minor league INF Frandy De La Rosa and cash. Blackburn made one start for Triple-A Sacramento this season. De La Rosa is hitting .253 over four minor league seasons in the Chicago Cubs' and Rangers' organizations.
Blackmon's shot was his first leadoff homer this season, after having hit a major league-best 10 as the Rockies' first batter of the game in 2016.
Arenado went 2 for 4 on his birthday. San Francisco manager Bruce Bochy turned 62 - with the loss, he's now 4-7 on his birthday while guiding the Giants.
Giants: OF Jarrett Parker was placed on the 10-day disabled list a day after breaking his collarbone by slamming into the fence while catching a fly ball. Bochy said Parker, who is hitting .143 in nine games this season, had surgery Sunday and will miss about 8-10 weeks.
LHP Steve Okert, recalled earlier Sunday by the Giants from Triple-A Sacramento to take Parker's place on the active roster, got one out in the eighth inning - retiring the only batter he faced on a comebacker to the mound. Okert, who also was recalled earlier this season but did not make an appearance, was in 16 games for the Giants last season, allowing five runs on 14 hits in 14 innings.
Rockies: After a day off on Monday, Kyle Freeland is scheduled to start Tuesday as Colorado continues its road trip at the Los Angeles Dodgers.
Giants: Matt Cain makes the start Tuesday at the Royals to open a seven-day trip. It will be San Francisco's first visit to Kansas City since the 2014 World Series.