Less than 24 hours earlier, Romo absorbed the decision in the Giants' 7-4 setback by allowing Colorado's five ninth-inning runs, a lapse partly attributed to Pagan's pair of throws to the wrong base.
For the Rockies, Barnes' blow offset a memorable Giants event. Pagan stroked a two-run, inside-the-park homer to give San Francisco a 6-5 walk-off win over the Rockies on May 25, 2013. That happened to be Pagan's last act as a Giant until late August, as an injured left hamstring scuttled his season.
Asked about the parallel between Barnes' high-speed trip around the bases and his, Pagan replied, "I'm not thinking about that."
No, ballplayers aren't much for irony. They prefer action to reflection. The Giants, who continued to possess baseball's best record, couldn't do much about losing five of their last six games, except for returning to AT&T Park on Sunday and striving to avoid a three-game series sweep.
"So many good things have happened to us," Giants manager Bruce Bochy said. "We've made some good comebacks. Then we hit a bump in the road. It's going to be important that we handle this well."
The Giants appeared destined for a better fate as Saturday's ninth inning began. Romo retired DJ LeMahieu on a first-pitch ground ball and erased pinch-hitter Troy Tulowitzki on a fly to center. Then Charlie Blackmon's opposite-field single to left, which Bochy referred to as a "bloop," prolonged the inning.
Up came Barnes, who slapped an 0-1 pitch to right-center field. Pagan appeared in position to cut off the ball, but it eluded him and skipped to the base of the outfield wall. Right fielder Hunter Pence scooped up the ball and flung it to second baseman Brandon Hicks, who rushed his throw just to have a chance at retiring Barnes. That didn't come close to happening. A thrilled Barnes scored easily as Posey stepped in front of home plate to accept Hicks' bouncing throw.
Pagan said he couldn't handle Barnes' hit due to its odd spin.
"I thought it was going to be a normal hop. But it kind of went a little bit to the right," Pagan said. "I did everything I've got to make the play. But what happened, happened."
Pagan, who made a difficult catch on Barnes' line drive to end the second inning, was shocked when he couldn't come up with the ball.
"It was a cold-water bucket for me," he said.
Romo shared Pagan's feelings.
"I'm just in disbelief, really, especially the way it went down," Romo said.
Searching for an explanation, Romo attributed the Giants' unraveling to the fickle nature of the sport they play.
"That's baseball," he repeated. Bochy used the same bromide to rationalize the defeat.
Of the four save chances in 24 opportunities Romo has blown this year, three have occurred against the Rockies. His ERA is 19.80 this season against Colorado, compared to 1.93 against all other teams. Asked what advantage the Rockies possibly could have on him, Romo said, "I think it's just familiarity, really."
Romo expressed faith in the Giants' ability to recover from this week, which has left them with a 4-5 record on their 10-game homestand entering Sunday's finale.
"I honestly believe that we're the hardest-playing team every day," he said. "I don't expect that to change the slightest bit. These guys are still trying. The effort is not the question. The confidence is not what we're questioning here."
The final out was questioned by the Giants, who believed that Pagan crossed first base safely after forcing out pinch-runner Tim Lincecum at second base. The Giants challenged the call, which was upheld after considerable deliberation.
"I guess they have to be conclusive," Pagan said. "You have to respect that."
Earlier, Buster Posey drove in a season-high three runs, delivering a two-run homer that forged a 3-3 tie in the fifth inning before lifting a sacrifice fly in the seventh that put San Francisco ahead.
"We had a lot of life and energy," Bochy said. "That's a tough one for these guys to lose because we fought back."