SAN DIEGO >> Kyle Harrison made a lot of major-league hitters look foolish through his first two major-league starts. But it was the 22-year-old lefty’s turn to get humbled Saturday in his third time taking the mound for the San Francisco Giants.

Harrison surrendered four home runs and took the loss as the Giants (70-66) fell to the Padres (64-73), 6-1.

Three of the long balls came within the first seven hitters Harrison faced before Garrett Cooper delivered the final blow, a three-run shot in the sixth, that ended Harrison’s night. The early barrage of homers, from Juan Soto, Xander Bogaerts and Gary Sánchez, echoed the way Tristan Beck began Friday night’s loss.

Harrison became the first left-hander in the modern era to strike out at least 40% of the batters he faced in his first two big-league starts, racking up an impressive ledger of victims, and he flashed the same swing-and-miss stuff Saturday. He powered a heater past Fernando Tatis Jr. in the first inning and finished with five strikeouts.

But baseball at its highest level is a game of adjustments, as the Giants have learned the hard way this year. Torrid starts for rookies such as Casey Schmitt and Luis Matos quickly turned tepid as professional pitchers learned how to attack them.

Harrison, despite his electric arsenal, is no exception.

“The league adjusts to you. They tend to do a better job the more they see you,” manager Gabe Kapler said before the game, using their opposition for comparison. “Blake Snell’s a decent example on the other side. As a young player, he had great stuff. The league’s adjusted along the way and he’s made adjustments back.”

Snell won the American League Cy Young with the Rays in 2018, going 21-5 with a 1.89 ERA, and is in contention for the National League honor this year. But in the four years in between, Snell suffered from inconsistency and posted a pedestrian 3.85 ERA.

On Saturday, the Giants had no answer for the hard-throwing lefty.

Snell, who lowered his ERA to an NL-best 2.50, could become the first player in history to lead the league in walks and ERA. He issued four free passes, bringing his season total to 89, and the Giants ran up his pitch count to 113 to knock him out after six innings.

But Snell, who is also second in strikeouts, punched out eight Giants hitters, and San Francisco stranded all seven runners who reached base against him. They were hitless in their first seven chances with runners in scoring position until Austin Slater doubled home Casey Schmitt in the ninth and left 11 men on base while striking out 12 total times.