SAN FRANCISCO — A week ago, Matt Vierling was still playing in double A, picking up three more hits in a victory for Reading. So imagine the outfielder’s surprise Friday, three days after getting promoted to triple A, when the Phillies added him to the 40-man roster and called him up to the majors.

“I didn’t expect it,” Vierling said Saturday upon joining the Phillies and picking up his first major-league hit, stolen base, and run against the Giants. “I didn’t expect it at all. I’d only been [in triple A] for 72 hours, maybe.”

But Vierling was among the hottest hitters in the Phillies’ farm system. He batted .345 with six doubles and six homers in 102 plate appearances in double A and went 5-for-12 in three triple-A games. Bryce Harper was impressed with Vierling in spring training, and president of baseball operations Dave Dombrowski must’ve liked what he saw this week as he made a tour of the team’s minor-league affiliates.

And with veteran outfielder Matt Joyce trying to play through a lower back strain, the Phillies decided to put him on the injured list and tap into Vierling’s hot streak.

In his first at-bat, as a pinch-hitter in the sixth inning, Vierling lined a single to right field against Giants lefty reliever Jarlin Garcia. With the Giants set to use lefty Sammy Long as an opener Sunday, there’s even a chance the 24-year-old right-handed hitter will make his first major-league start, according to manager Joe Girardi.

“He’s been playing really well at both levels, so we called him up,” Girardi said. “We feel good about what Vierling’s done. It gives us some depth.”

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Vierling is the fifth player who has been added to the Phillies’ evolving 40-man roster since opening day, joining fellow outfielders Odúbel Herrera and Travis Jankowski, versatile Luke Williams, and pitcher Enyel De Los Santos. The Phillies had an available spot because Chase Anderson doesn’t count against the 40-man roster while he’s on the COVID-19 restricted list.

The Phillies called up Williams 10 days ago on the heels of a hot start at triple A and a week in which he went 8-for-18 to help Team USA qualify for the Olympics. Entering Saturday’s game, he was 9-for-22 (.409) with three doubles and a homer in nine major-league games.

With Vierling, the Phillies are hoping to ride a similar wave.

“They come up with confidence, and they come up with not sitting a lot,” Girardi said. “I think there’s an advantage to that, yes. And the league doesn’t really know them that well yet. You could pull up [scouting] stuff on everybody, but there’s not a lot of history.”

Vierling was the Phillies’ fifth-round draft pick in 2018. He struggled in 2019 at high-A Clearwater and didn’t play last season because of the pandemic. But he went to instructional league last fall and big-league camp in spring training and built a foundation for his solid start to the season.

“Quarantine was pretty productive for me,” said Vierling, who worked on his swing at home in St. Louis. “I got to see how it worked in instructs and big-league spring training and just took that approach into the alternate site and then into the season. I just had so much confidence. Been feeling really good about my approach and where I’m at.”

The Phillies can offer opportunities for young outfielders, too. If they decline their options on Herrera and Andrew McCutchen, they may be searching for a center fielder and left fielder in the offseason. It would be helpful to know if internal options such as Vierling, Mickey Moniak, and Adam Haseley are potential solutions.

Vierling has made 75 starts in left field, 50 in right, and 49 in center in the minors. This season, he made 15 of his 27 starts in center.

“I love center field,” said Vierling, whose parents hopped a flight from St. Louis to San Francisco early Saturday. “I feel like I can use my athleticism the most there. But wherever I could be to help the team win, whether that’s left, right, or center, I feel comfortable anywhere really out there.”

Joyce is 5-for-50 (.100) with 10 walks and 14 strikeouts so far this season. He grounded out as a pinch-hitter in the fifth inning of Friday night’s 5-3 loss to the Giants.

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Best vs. Mets

In a move designed to make sure their three best starting pitchers will face the division-leading Mets next weekend in New York, the Phillies shuffled the rotation to have Zach Eflin start Sunday, on regular rest, in the series finale against the Giants.

The Phillies could have opted to give Eflin additional rest, as they did earlier in the month. Instead, they will skip rookie Spencer Howard’s turn and have Eflin start on four days’ rest.

Aaron Nola, who faced the Giants on Saturday, is lined up to start Friday in New York. He’s scheduled to be followed by Eflin next Saturday and Zack Wheeler on Sunday. Wheeler and Vince Velasquez will start Tuesday and Wednesday nights, respectively, at home against the Washington Nationals.

Howard will be available out of the bullpen, according to Girardi. The Phillies will need Howard to start one game of Friday’s doubleheader against the Mets.

Extra bases

The Phillies placed catcher Andrew Knapp on the seven-day concussion list, as expected, and called up Rafael Marchan from triple-A Lehigh Valley. Knapp got hit square in the mask by a pitch Friday night. “He said he doesn’t feel too bad,” Girardi said. “He feels it more in his jaw. But he doesn’t look too bad today.” ... Williams in the first Phillies player since at least 1900 to start his first four major-league games at four different positions (center field, third base, shortstop, second base), according to the Elias Sports Bureau.