SAN DIEGO -- The adjustments inherent in the always evolving battle of pitcher vs. hitter often occur on a macro scale. The hot hitters find pitchers approaching them differently. A slumping pitcher might work for weeks on a mechanical adjustment or a new pitch to get back on track.

Sometimes, however, the adjustments occur on the fly, in the crucible of a game itself.

Such was the case on Thursday night as the Nationals fell 5-4 in the opener of a four-game series against the Padres at Petco Park. The Nats saw their four-game win streak halted despite scoring four runs before Patrick Corbin threw a pitch.

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Padres starter Joey Lucchesi made a quick adjustment to avoid getting knocked out early, and Padres batters also altered their approach as Corbin battled to right his mechanics.

Knowing Corbin wasn’t consistent with his fastball, Padres batters stopped swinging at sliders out of the zone, negating one of the left-hander’s key weapons. They scored twice in the second inning and three times in the fifth to erase the four-run deficit.

“I just fell behind; I wasn’t throwing strike one,” said Corbin, who has followed a complete-game shutout with two subpar outings.

Corbin threw 101 pitches while allowing five runs (three earned), five hits and five walks in five innings. He said he was flying open in his delivery, causing his sinker to dive away and out of the strike zone. And pitching behind in the count, he couldn’t get the Padres to chase that slider.

“I just didn’t make that adjustment quickly enough,” he said. “You can’t walk five guys. I allowed too many baserunners.”

Corbin’s effort comes on the heels of a 2 2/3-inning outing Friday at Cincinnati, where he was touched for eight runs (six earned) and 11 hits against the Reds. He said the mechanical issues are correctable.

“We’ll get him straightened out,” manager Dave Martinez concurred. “He’s a veteran guy. He’s done this before. He’ll get some work in this week and get back on track.”

Hunter Renfroe initiated the Padres’ comeback with a mammoth, 442-foot two-run homer in the second inning, connecting on a 93 mph fastball on a 3-1 count. They took the lead when they benefited in the fifth from two walks, a wild pitch and a bases-loaded error.

With nobody out, Manny Machado hit a spinning ground ball to the right of shortstop Trea Turner, who elected to try to force out Fernando Tatis Jr. at third base. Turner’s throw and Tatis arrived at the base as third baseman Anthony Rendon tried to get his feet set to field the throw. Instead, Rendon missed the throw and was charged with an error. Lead runner Manuel Margot and Tatis scored, and Wil Myers advanced from first to third. That tied the game 4-4 and set up Franmil Reyes go-ahead sacrifice fly.

“It was a slow-hit ball, kind of a spinner,” Turner said. “I had momentum going to third, so I thought that was the right play. Looking back at it, if I make a better throw, we probably get out of that inning with the lead. … I don’t think it was the wrong play. It was the right play, and I stick by it.”

That play would not have had such magnitude had the Nationals’ offense been able to add on after the four-run first inning. Howie Kendrick had a two-run single and Brian Dozier a two-run homer.

The Nationals loaded the bases with two outs in the following inning and were on the verge of knocking Lucchesi out of the game on his 26th birthday, but the left-hander retired Juan Soto on a grounder and got nine of the next 10 batters, as well. With four perfect innings from the Padres’ bullpen, the final 20 Nats batters went down in order.

“He started mixing his pitches,” Martinez said. “Credit to him. We just couldn’t get anything going. … He kept them in the game.”

Said Turner: “He settled in, and we couldn’t get to him again.”