SAN FRANCISCO — Rock-bottom Rockies.

Just when it seemed things couldn’t possibly get any worse, they did.

After dropping an 18-inning game to the Giants that started on Friday and leaked into the wee hours of Saturday morning, the Rockies lost 5-2 to the Giants on Saturday afternoon at Oracle Park.

Colorado has now lost 12 of its last 13 games and its 3-12 start is the worst beginning to any season in franchise history. The magnitude of the slide is being felt throughout the clubhouse.

“Something’s got to change, obviously,” veteran center fielder Ian Desmond said. “Something’s got to be shaken up, something’s got to be done differently. We need to figure it out.”

Asked if he agreed with Desmond’s assessment, star third baseman Nolan Arenado said: “Absolutely.”

Exactly what changes should be made are not clear, but Arenado noted that the Giants won the game by moving batters along, hitting sacrifice flies and playing sound baseball — things the Rockies have not been doing consistently.

“We are not doing the little things, and on top off that we are not having good at-bats,” Arenado said.

Veteran first baseman Mark Reynolds, who hit a solo home run off Giants ace Madison Bumgarner to close the gap to 3-2 in the seventh inning, said the Rockies must begin playing with a greater sense of urgency.

“We have plenty of time to snap out of this, but you don’t want to get too far behind,” he said. “Every time I talk to you guys, it’s like, ‘We’ll be fine, we’ll be fine.’ But at some point, you have to hit that panic button. You have to do the little things right. Getting the lead runner, holding the lead runner … we are not doing that.”

No. 1 starter Kyle Freeland was pulled from the game after five innings because of a blister on the middle finger of his left hand. He said after the game that he doesn’t consider the blister to be a major problem, adding that it didn’t affect his performance.

“I’ve had the blister before, so I’m not worried about it, because we know how to manage it,” said Freeland, noting that the blister first appeared in the second inning.

Frustration erupted in the sixth when Bumgarner struck out Arenado looking to end a rally with Garrett Hampson stranded on third base. Arenado — who has not hit a home run in 60 at-bats this season and has only six RBIs in 15 games — went ballistic, tossing his helmet and bat, and nearly got ejected by home plate umpire D.J. Reyburn. Arenado had a reason to lose his cool. The called third strike was clearly inside.

“I was just frustrated,” said Arenado, who battled back from an 0-2 count to make it 3-2. “I was facing a really good pitcher, I had a full count and I had a good at-bat and I felt like I walked. We all saw the replay, so I don’t need to speak on it.

“He’s a fine umpire and he’s just doing his job. He missed it, which is frustrating because we had a man on third.”

Bumgarner pitched seven-plus innings, getting lifted after Chris Iannetta opened the eighth with a double. The left-hander allowed six hits, struck out seven and walked none. He improved to 9-2 with a 1.94 ERA in 16 career starts vs. Colorado at Oracle Park.

“He’s a great competitor and he makes pitches,” manager Bud Black said. “He’s got deception and he’s still got enough stuff to beat bats and his secondary pitches have improved over the last number of years.

“We knew what we were in for and we went after him and stressed him a couple of times but we couldn’t break through.”

The Rockies finally put a run on the scoreboard in the sixth with Hampson’s RBI double off Bumgarner to score Charlie Blackmon. It was Colorado’s first run in 19 innings, going back to their two-run fourth inning of the 18-inning loss.

Freeland, not close to matching his stellar performance from last season, was tagged for three runs on nine hits. Kevin Pillar’s solo home run to left field in the fifth turned out to be the difference in the game. It was Pillar’s fourth homer of the season.

“I was trying to steal a strike with a curveball,” said Freeland, now 1-3 with a 5.40 ERA. “The second or third time through the lineup, I was trying to get him a little off-balance and I threw a curve and he was ready for it.”

San Francisco staked a 2-0 lead in the third on a sacrifice fly by Pillar and an RBI double by all-star catcher Buster Posey — his first RBI of the season.

The Giants added two insurance runs in the eighth off relievers Seunghwan Oh and Mike Dunn.