NEW YORK -- You think Triston Casas enjoys the electricity of Red Sox-Yankees?

Boston’s No. 2 prospect, who is trying to position himself to be the starting first baseman for next season and for several years after that, belted his fourth career homer on Saturday at Yankee Stadium.

Three of those homers have come against the Yankees. This was the second long ball in the last three days for the big left-handed hitter. The only regret for Casas is that the Red Sox have lost the first three games of this four-game series, including Saturday’s 7-5 defeat.

“The crowd is electric,” said Casas. “Playing here is everything that everybody says it is. I don’t know if any other stadium compares to this one, especially this environment, with the rivalry and stuff. It’s been a lot of fun coming here, playing and being able to contribute, most importantly.”

The homer Casas hit Saturday in the top of the second inning against Domingo Germán was an opposite-field missile that left his bat at 101.7 mph and traveled a Statcast-projected distance of 375 feet.

Going oppo at Yankee Stadium isn’t all that easy for a lefty.

“No, I don't think I hit one that way,” quipped Red Sox manager Alex Cora, who was a light-hitting lefty in his day. “It was a good swing. A really good swing.”

Though you wouldn’t know it by his .130 batting average, Casas is starting to come around at the plate.

His patience is paying off. Casas reached base in four of his five plate appearances on Saturday, including one walk with the bases loaded and another that loaded the bases while the Red Sox were trying to mount a rally in the top of the ninth.

Casas has a noticeably disciplined approach for a 22-year-old who is starting to play at the highest level. He has 12 walks in his first 58 career plate appearances.

“I think I was a little jelly-legged my first 40-something ABs, but today, it felt good getting on base that many times,” said Casas. “I came up in a couple of big spots and was able to grind out some at-bats and get on base.”

What has changed for Casas of late?

“I think in the beginning, I was really looking at the amount the pitches were moving and it was working to my disadvantage,” Casas said. “The fact that they’re moving so much really helps me try to focus on one part of the plate, and if it starts down the middle, pretty much guys are making it move and it’s going to be a ball. I’m really focusing on where I want it to start versus where I want it to end, and that has been the biggest adjustment I’ve made.”

Casas surmises that by showing pitchers that he’s happy to take walks whenever he can, he is going to start getting more pitches he can offer at and do damage with.

“I think discipline comes with a trickle-down effect,” Casas said. “I don’t think I’m going to come into the league and they’re just going to attack me with fastballs, and I'm going to hit home runs and they’re going to be scared to pitch to me. I think they’re going to work the edges and try to see how much I’ll chase, how far I'll go off, and then if I keep chasing after it, they’re not going to attack me with anything in the zone. I think if I display that discipline for the edges, they’ll come to the middle of the zone eventually.”

How far back in his baseball life has Casas been so selective? It turns out it goes back very far, as in childhood.

“It’s definitely something that I’ve always worked on,” Casas said. “If you don’t swing at good pitches, you’re just going to be chasing and you’re going to be off-balance, and they’re never going to attack you. Yeah, it’s definitely been something that some of my early coaches and my dad were really hard on me to swing at good pitches and pick the right ones to hit.”

Though the hits -- unlike the walks -- have been sparse for Casas so far, he has made them count.

Casas, who got his promotion to the Major Leagues on Sept. 4, has four homers and two singles thus far.

“Eventually, yeah, I think I'll find some grass. I think it will all even out,” said Casas. “I’ve got more homers than singles. That’s a little weird. It’s not exactly how I imagined my first six hits going. But I know I can count them on two hands now.”