Arenado reached base five times, starting with his 10th home run. He was denied his 11th in the second inning when his blast down the line in left was ruled foul by third base umpire Ted Barrett. The call was upheld on a crew chief review.
"Today was a great day but you want as many home runs as you can get," said Arenado, who has hit all of his home runs since April 14. "It's a tough call for Ted, I get it, but I just don't think the ball lands there if it's foul. I think if it was the other side of the pole it lands in the stands but it lands on the stairs."
Ian Desmond and Mark Reynolds also homered on a cold, sometimes wintry day at Coors Field. The game took 3 hours, 56 minutes in 40-degree weather. The announced temperature at first pitch was 39 degrees and a steady snow fell in the first inning. That didn't stop Arenado and Reynolds from homering on consecutive pitches.
"The first at-bat I was having trouble seeing," Arenado said. "Luckily I was able to barrel that one. It definitely wasn't fun out there. It was a long game, we wish we didn't have that long of a game in that type of weather but it was a battle."
Colorado won despite two home runs and a career-best six RBIs by Giants first baseman Tyler Austin. He hit a two-run homer in the third inning and a three-run shot in the sixth off Bryan Shaw (2-0) to tie the game at eight.
Those were Austin's first two homers of the season. "To get the first one out of the way is very big," he said. "Hopefully there are many more to come." Iannetta put Colorado back in front against reliever Tyler Beede (0-1) in the sixth, and pinch-hitter Daniel Murphy singled off Austin's glove to put the Rockies ahead 11-8.
Both teams scored a run in the eighth and the Giants got two more in the ninth off Wade Davis before he struck out Stephen Volt for his sixth save. The Rockies built a 7-0 lead in the second inning off starter Derek Holland, who lasted just 2 2/3 innings. Arenado and Reynolds went back-to-back in the first and Desmond capped a four-run second with a two-run homer.
"I thought the weather played a part in it," manager Bruce Bochy said of Holland. "He was without his breaking ball. He didn't have a feel for it and it's hard to pitch here without it." The Giants rallied for five runs — three earned — off starter Kyle Freeland and tied it in the sixth.
TRAINER'S ROOM Giants: LHP Drew Pomeranz was placed on the 10-day injured list with a lat strain. Pomeranz lasted just 1 2/3 innings in his previous outing. San Francisco recalled C Aramis Garcia and Beede in corresponding roster moves for Pomeranz and C Buster Posey.
Rockies: Manager Bud Black said LHP Jake McGee and RHP Chris Rusin were scheduled to pitch rehab assignments with Triple-A Albuquerque on Thursday. McGee (left knee sprain) was scheduled to start the game and Rusin (mid-back strain) was expected to come in later in the game.
POSEY OUT WITH CONCUSSION The Giants placed Posey on the seven-day concussion list prior to Thursday's game. Posey said he was hit with a foul ball Sunday against Cincinnati and felt the effects since despite playing in Tuesday's 14-4 win over the Rockies.
"They are going to take extra time to find out how I am," Posey said. "When they examined me (Wednesday) they felt I should have felt more normal after three days. When you are dealing with the brain, you've got to be cautious."
UP NEXT Giants: RHP Dereck Rodriguez (3-4, 5.75) opens a three-game home series against the Cincinnati Reds on Friday night. Rockies: RHP German Marquez (3-2, 3.46) makes his fifth home start of the season and ninth overall against the San Diego Padres on Friday night.
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