SAN DIEGO -- Not even the best Major League pitcher can have electric stuff in every outing. It’s the ones who learn to live off the grid, so to speak, who survive.

Giants rookie Kyle Harrison went to the mound for his third MLB start Saturday night at Petco Park without the electric fastball that was on display in his previous outing. And the 22-year-old left-hander surrendered four home runs in a 6-1 loss to the Padres that left the Giants in a three-way virtual tie for the third and final National League Wild Card spot.

• Games remaining (26): at SD (1), at CHC (3), vs. COL (3), vs. CLE (3), at COL (4), at AZ (2), at LAD (4), vs. SD (3), vs. LAD (3)

• Standings update: The Giants (70-66) are tied with the D-backs (70-66) and Reds (71-67) for the third and final NL Wild Card spot. The Marlins are one game back of that trio. The Cubs hold the second NL Wild Card spot with a two-game buffer over the teams tied for the third.

“I didn’t execute four pitches,” Harrison said. “Unfortunately, they went for home runs that damaged my chance to give us a chance to win a game. Definitely not one of my best.”

Mind you, the stuff Harrison had might not have been dominant, as it was Monday against the Reds in an 11-strikeout performance, but it was plenty good enough to win in the big leagues. That was the message delivered by his teammates, by his manager and even by the opponent Saturday.

“He’s going to be good at what he’s doing for quite a while,” Padres manager Bob Melvin said. “… There are some challenges that he presents with his arm angle, his extension. Early on, he got some fastballs by us when we were looking for fastballs.”

Added Giants manager Gabe Kapler: “I can’t stress this enough -- he attacks the strike zone, he throws his pitches for strikes. There are going to be a lot of times he’s pitching in the sixth, seventh and eighth innings of games.

“Not trying to discount the outcome -- it wasn’t a great outcome for the Giants and Kyle’s disappointed about that -- but I’m very confident in him going forward. I’m very confident that this, what he did tonight, if he does it over and over, it will work and it will beat a lot of good Major League hitters.”

Harrison allowed three solo home runs -- on three pitch types -- in the first two innings. Juan Soto hit a fastball in the first. Xander Bogaerts (slurve) and Gary Sánchez (changeup) connected in the second.

Harrison then showed some “off the grid” ability by putting up zeros over the next three innings to ease the bullpen burden and keep the Giants in the game even as Cy Young candidate Blake Snell was in top form for the Padres. Harrison, however, yielded a fourth homer when Garrett Cooper golfed a 91.8 mph four-seamer for a three-run drive in the sixth inning.

That was Harrison’s 91st and final pitch. It matched the number of pitches he threw on Monday, when he tossed 6 1/3 scoreless innings against Cincinnati. This time, he struck out five over 5 2/3 innings and allowed six runs. Still, he generated nine swings-and-misses with his fastball, 12 overall.

In the top of the seventh, catcher Patrick Bailey huddled with Harrison in the dugout. The message?

“I was really proud of how he handled some adversity in the early innings,” Bailey said. “I thought he threw the ball well in the middle innings. It’s not going to happen too many times that you give up four homers. For the most part, he stayed aggressive.”

The Giants weren’t giving Harrison pep talks simply for the good of his long-term development. Three starts into his MLB career, he’s already a key cog in the team’s pitching plans down the stretch of a playoff race.

His next start is likely to come at home next weekend against the Rockies. The pep talks Saturday were the first step toward a bounce-back outing.

“It’s kind of a ‘flush it’ mentality,” Harrison said. “They’re supporting me and telling me my stuff’s great. You’ve got to believe that if you’re a pitcher out there. I’m really going to go after the next guys I face. I’m really thankful we have a great clubhouse, and the guys have supported me.”