SAN FRANCISCO -- Kyle Harrison's Major League debut is not that far in the past, but from the way he talks about it, it may as well have been ages ago.

"I wish I still had the kind of adrenaline that I had back then," he said with a laugh.

"Back then" is last Aug. 22, when Harrison got his first taste of big league action at Citizens Bank Park against the very same Phillies he faced in the Giants’ 6-1 loss on Wednesday afternoon at Oracle Park.

Nine months ago, Harrison was a Minor Leaguer and San Francisco’s top pitching prospect. Now, the 22-year-old left-hander has 19 big league starts under his belt and is accustomed to taking the ball in the Majors every fifth day.

As Harrison knows by this point, everyday life in MLB comes with plenty of ups and downs, just as he experienced in Wednesday's loss. Following two games in which Giants relievers combined to cover 15 innings -- five on Monday and 10 in Tuesday's bullpen game -- Harrison had to grind to complete five.

It was a gritty outing for the left-hander, who had to navigate heavy traffic after giving up a career-high 12 hits and one walk. He allowed four runs -- one shy of his season high -- with the brunt of the damage coming on Kyle Schwarber's leadoff home run in the first inning and Nick Castellanos' two-run blast in the fifth. Cristian Pache also notched an RBI single off Harrison in the second.

"I feel like my command was pretty good today," Harrison said. "I feel like I was able to kind of put it in spots that I wanted. But you know, I think too many strikes that I kind of stressed. Especially when I was ahead and just kind of let them back in. … Any time you look up and see 12 hits, it's not a good day."

The Giants snapped a nine-game winning streak at Oracle Park against the Phillies, but they were still able to take two out of three games from the team with the best record in the Majors. Not to mention, San Francisco was swept in four games by Philadelphia earlier this month.

While the Giants' bats fizzled on Wednesday, there was some excitement midway through the game when the benches cleared after Phillies star Bryce Harper took objection to consecutive up-and-in fastballs from Harrison in the fourth inning.

Harrison had struck Harper out twice already, and Harper had not had a productive road trip at the plate. He didn't get a hit in the San Francisco series until the eighth inning on Wednesday.

"[Frustration] probably had something to do with it," Harrison said. "But I don't know. I'm just a kid trying to throw strikes and get him out, you know?"

When the benches cleared, the initial call on the field was that Harrison had hit Harper. A review found the ball hit the knob of Harper's bat, and so the at-bat resumed. Harrison settled back in and induced a groundout.

"When Bryce Harper gets pissed off and yells at you, I've got to imagine when you're a young guy, that's pretty terrifying," said third baseman Matt Chapman, who talked to both Harrison and Harper as the situation deescalated. "I was just trying to calm him down, make sure, 'Hey, don't get it in your head. Just try to make your pitch and be maybe a little more fine.'"

For what it's worth, Harper didn't take the situation personally once he had some time to calm down.

“He didn’t mean to, just sinkers in," Harper said. "I wasn’t really that mad.”

Chapman wasn't the only one of Harrison's teammates who noticed that the young left-hander was able to keep his composure in a tense situation. Harrison also received praise from his catcher.

"I think he calmed down very nicely," Curt Casali said. "Me and him both knew we weren't going to throw another fastball right away. Let's throw a slider and get back in the count. See where his head's at. He made three good pitches right away and got him out.

"It's not easy to do, especially when your heart rate gets going. Made a mistake, didn't mean to. It was impressive that he was able to come back the way he did. That's what pros do."

While it wasn't particularly a day to remember for Harrison, it's all part of his development as a big leaguer, both on and off the mound.