JUPITER, Fla. — This spring is filled with adjustments for Kodai Senga, who has never pitched in Major League Baseball, with a pitch clock or within a five-man rotation.

In his stateside debut, the Mets right-hander showed he is still adjusting and said he felt “rushed” by the newly introduced pitch timer — but demonstrated that opposing hitters would have to do some adjusting to him, too.

After a wild start, Senga used his ghost forkball to record a strikeout, touched 98.6 mph with his fastball and pitched two innings in which he allowed a run in a successful initial Grapefruit League outing Sunday for the Japanese star.

The only hit Senga surrendered was a second-inning home run to St. Louis’ Tres Barrera, who hammered a hanging curveball. Senga exited after 42 pitches in which he exhibited intriguing stuff — four of his five pitches drew a swing-and-a-miss, and his fastball averaged 96.9 mph — but also struggled with his location.

Senga, who said he was excited but not nervous, walked the first two batters he faced. Of his first 16 pitches, just five were strikes.

“[I felt] very rushed in the beginning,” Senga said through an interpreter after the 7-1 Mets win over the Cardinals at Roger Dean Stadium. “I thought if I had more time to spare at the end, I could get settled in. But [the clock] just kind of ended up rushing everything, including my mechanics.”

With those runners on first and second in the first, he induced a pop-up from Paul Goldschmidt and a flyout from Nolan Arenado before Senga conjured the ghost.

Jordan Walker became the first victim of a pitch known as the ghost forkball (but unfortunately registers on MLB’s Statcast as a splitter). With two strikes, Senga turned to his signature offering, which starts high and disappears. Walker swung over the top of the 83 mph ghost.

Senga only threw his nastiest pitch twice.

“[There have been] a lot of meetings inside on what pitches to use,” said Senga, who could be saving the ghost fork for the regular season.

The 30-year-old, whom the Mets signed to a five-year, $75 million contract this offseason, might be the most interesting player in camp. The righty developed into a superstar in Japan, where he pitched in 22 games last season in the Japan Pacific League and posted a 1.94 ERA.

Starting pitchers in Japan pitch once a week (with higher pitch counts), so MLB life will take some figuring out. As will the pitch clock. Senga had no violations in his debut, but it dominated his thinking and probably played a role in his location.

“I was very excited to face those guys,” Senga said of a strong Cardinals lineup. “But once I was up there, my mind was kind of filled with the pitch clock, and I couldn’t enjoy it as much as I wanted to.”

Buck Showalter was not worried after one abbreviated exhibition start.

“He’s a good athlete and smart. He’s going to figure it out,” the Mets manager said. “He had to make adjustments in Japan to things. Baseball felt good in his hand, and it’s a good outing to build on.”

After a difficult, 27-pitch first inning, Senga seemed more comfortable for the second. A high, four-seam fastball struck out Nolan Gorman and another got Alec Burleson to ground out. After Barrera’s homer, Masyn Winn popped up a good curveball.

Senga’s arsenal also includes a cutter and goes five pitches deep. The stuff looked high-octane, and it’s possible the key will be harnessing it — and adjusting to a pitch clock that had him rushing back to the mound after each pitch.

“Good fastball, thought the slider was pretty good,” said Arenado, who saw fastballs, a curveball and a slider. “Obviously in that first inning he was a little erratic I guess. But seems like he’s got plus stuff. Seems like he’s going to be really good with them.”

— Additional reporting by Jon Heyman