SAN FRANCISCO -- The D-backs entered Tuesday feeling energized after a gritty series-opening win in San Francisco. But a challenging first inning set the tone in Arizona's 13-0 loss to the Giants at Oracle Park, putting the team in an early deficit it could not overcome.

The season-long funk continued for left-hander Dallas Keuchel, who looked as if he might be on the verge of turning things around with a quality seven-inning start in his previous outing. Instead, he had one of his toughest outings since joining the D-backs earlier this month, allowing eight runs (seven earned) over 2 1/3 innings.

"This was a grinder, there's no doubt about it," Arizona manager Torey Lovullo said. "We didn't make some key plays early on. I thought that could have changed the early innings, but we didn't make them, we didn't make pitches. It just got out of hand and spiraled out of control quickly."

Keuchel was shaky from the get-go, allowing three of the Giants' first four batters to reach base. It seemed like Keuchel was going to escape with only one run allowed, though, as he got San Francisco's David Villar to hit a seemingly routine fly ball to right field with two on and two outs.

That's when things began to go downhill.

Right fielder Jake McCarthy lost the ball in the sun and tripped as he tracked it down, falling to the ground as it skipped past him to the outfield wall. The Giants' two baserunners both came around to score, as the speedy Villar raced around second base and slid into third.

In the meantime, McCarthy had recovered the ball and relayed it to second baseman Sergio Alcántara, whose throw to third skidded past a diving Josh Rojas and lodged itself into the Giants' dugout. The errant throw gave Villar an extra base, and he came away with a Little League home run.

A clean play on the fly ball would have ended the inning. Instead, the D-backs had suddenly given up a four-spot to the Giants.

"I would have liked that play to be made," Keuchel said, "but at the same time, I've got to be better in order for that play not even to happen. It's on me, and I didn't really do a good job in getting their guys out with some early contact."

Keuchel has always relied on getting outs on balls in play, which works as long as the defense behind him can field cleanly. That hasn't always been the case in 2022, which began with him still on the White Sox. Entering Tuesday, the defense behind Keuchel had posted minus-six Outs Above Average this season, which ranked 11th worst in the Majors (minimum 100 attempts).

The White Sox cumulative minus-10 OAA is tied with the Brewers for the eighth worst in MLB, while the D-backs had recorded an even zero OAA behind Keuchel entering Tuesday.

Another metric that indicates defense has factored into Keuchel's tough 2022 is the difference between his ERA and his expected ERA. Entering Tuesday, the difference of 3.14 between Keuchel's ERA (7.63) and his xERA (4.49) was the largest in the Majors among pitchers who had allowed a minimum of 150 balls in play. Keuchel's xERA is still a touch high, but the differential does signal that his ERA should be lower based on the contact he induces.

Defense can't erase home runs, though, and Keuchel gave up a season-high three long balls on Tuesday.

The D-backs' first trip to San Francisco this season has fluctuated wildly between soaring elation and crushing deflation. But just as the momentum shifted between the first two games of the series, Lovullo knows the same can be true for Wednesday's rubber game.

"We've got to be resilient," Lovullo said. "I think that's one of the key characteristics here. We do things in a very uncommon way, and we've just got to keep pounding. We've got to be ready for a quick turnaround."