SAN FRANCISCO -- It’s easy to see why the Padres dream of Dinelson Lamet one day sitting toward the front of their rotation. The 27-year-old right-hander has all the pieces.

The high-90s fastball with movement. The slider that bites hard. The curveball that falls off the table. Heck, Lamet even looks like an ace -- a muscular right-hander with a chiseled frame and a self-certain demeanor.

At various points in his career, Lamet has put those pieces together. But never for longer than a start or two. Long enough to tantalize the Padres. But never long enough to assert himself as the front-line arm they think he could be.

In an 8-3 loss to San Francisco on Friday night at Oracle Park, Lamet once again presented a fascinating juxtaposition. He struck out 10 Giants, surrendering only three hits. But two of those hits left the ballpark, and Lamet’s evening was done after 95 pitches and just five innings.

• Box score

“I could've been a little bit better outside of the couple pitches that I threw to the hitters that hit the home runs,” Lamet said. “But overall, I thought it was a positive outing.”

For the most part, it was. Lamet fell victim to some poor Padres defense at the outset. His first pitch to Giants leadoff man Mike Yastrzemski was a hard ground ball toward first baseman Eric Hosmer.

The ball went under Hosmer's glove and down the right-field line where Hunter Renfroe tripped as he fielded it, allowing Yastrzemski to cruise into third base. It was the Padres’ 99th error of the season -- the most in the National League.

“That's a play that Hoz would expect himself to make that he makes all the time,” said Padres manager Andy Green. “He just didn't make it.”

Two pitches later, Lamet left a fastball over the inner half of the plate, and Brandon Belt pulverized it over the right-field wall for a two-run home run. Lamet settled in from there, striking out Evan Longoria -- for the first of three times -- with a 3-2 slider. Over the next two innings, Lamet recorded all six outs via strikeout.

“Ten punchouts, two walks, and he can probably go a little bit deeper in the game if some things go his way,” Green said. “He threw the ball well today.”

Madison Bumgarner threw it better. The Giants lefty stifled the Padres’ offense with nine strikeouts over seven innings of four-hit ball. Manny Machado’s solo homer in the fourth inning -- his 28th of the season and the first of his career against Bumgarner -- was the only run allowed by the veteran left-hander.

The Giants answered an inning later. Lamet left a thigh-high fastball over the middle of the plate, and Yastrzemski lifted it to the opposite field. Padres left fielder Wil Myers seemed to have a read on the baseball. It carried into the first row.

To be sure, Lamet’s pitch wasn’t good, and Yastrzemski did enough to hit it out. But there’s an obvious element of luck on a batted ball with a .210 expected average that lands beyond the fence.

“That looked like a routine flyout to left field,” Green said.

The Giants did most of their damage against a beleaguered San Diego bullpen, scoring five times against left-hander Robbie Erlin. Machado tacked on a late double, and he finished 2-for-4. But the rest of the Padres offense was quiet, save for Hosmer's RBI single in the ninth.

As for Lamet, Friday marked his 10th start since he returned from Tommy John surgery last month. He notched a 5.09 ERA in the first five outings. His 3.54 mark in the last five is more than a run and a half better.

“Where he came from at the start, his first few outings to now, he's making a ton of progress,” Green said. “He had a hard time commanding anything early on. ... I thought he was solid today.”

Hard to argue with Green’s assessment. But Lamet’s ceiling is a lot higher than “solid.”

So how does he reach it?

“It's about my preparation,” Lamet said. “Prepare, attack, make sure my gameplan is ready. Whatever pitches I might have not done the best on in my last outing, make sure I fix that and correct it going into my next outing.”