The rookie outfielder hit a solo shot in the second inning against the Padres. ​

In his first trip to the plate on Sunday, Phillies outfielder Nick Williams took a hefty swing at the first pitch he saw — a 90 mph fastball — and knocked it 334 feet for his first major-league home run.

The ball arced into the left corner of the stadium, landing in the first row, and the scattered crowd at Citizens Bank Park cheered as the rookie made his solo lap around the bases. The second inning blast was the first of six for the Phillies, who dominated the Padres 7-1. It also capped off a series of firsts for Williams, who is finding his place in his first 10 days in the major leagues.

“I think the adrenaline is still going,” Williams said. “I don’t think that could ever go away honestly at this level.”

In his short time with the Phillies, Williams moved from a designated hitter to fifth and then third in the batting lineup. His rapid climb on the roster reflects the flexibility of Phillies’ management, which is still searching for answers to the summer’s offensive struggles. And, Williams has taken full advantage of his opportunity, notching nine hits, including two doubles, and one RBI in his first 32 at-bats.

On June 16, general manager Matt Klentak said that Williams was putting the “finishing touches” on his game at Lehigh Valley.Williams had been playing for the IronPigs, batting .323 with 11 home runs and 28 RBIs from May 17 to June 13. The 23-year-old’s success caught the attention of the Phillies.

Williams was called up two weeks later, and he took the field in a Phillies uniform for the first time on June 30 against the Mets. After going 1-for-3 in that first game, Williams continued to grow, smacking doubles against the Pirates and the Padres.

Sunday wasn’t a flawless performance for Williams. He was tagged out trying to steal second in the fourth inning. He flied out in the sixth and grounded into a double play in the eighth. Still, the rookie says he feels at home at the plate.

“In the box, I really haven’t felt uncomfortable at all since being called up,” Williams said. “You’re facing the best. Today, with (Padres pitcher Trevor) Cahill, I’d heard about him for years, even before I was drafted. You hear these named guys and then you actually get to face (them). It’s cool.”

Two balls now rest in Williams’ locker: one in a plastic cube and one still fresh from Sunday’s victory. The first is the ball from his first hit, a single from that June 30 loss at the Mets. The second — the home run ball — he got after forking over a signed bat, glove and a pair of cleats to the fan who caught it.

The Phillies now have four days to rest during the All Star break, but Williams said is anxious to get back on the field.

“I kind of wish the All Star Break wasn’t now,” Williams said. “I want to keep going. I’ve been loving this experience and this grind up here. It is a grind. I think I’ve been facing 95 (mph)-plus on every starter, but . . . it’s great to do it. I’d take it every day.”