All along, Red Sox officials maintained they would use the seventh overall pick in the amateur draft to select the best available player, regardless of position, rather than to address a specific need.

Apparently, nobody believed them.

Most draft pundits expected the Sox to take a power hitter in the first round Thursday night. But after outfielder Clint Frazier and third baseman Colin Moran were scooped up by the Indians and Marlins, respectively, the Sox picked Indiana high school left-hander Trey Ball, even though touted outfielder Austin Meadows was still on the board.

“We’re just basically taking the best player,” scouting director Amiel Sawdaye said on a conference call yesterday. “I know that’s something we say all the time, but it just worked out. The way the board shaked out, Trey Ball was the best player available.”

General manager Ben Cherington said the Red Sox eyed Ball since last summer, a pivotal time in the scouting process because the weather in Indiana was considerably cooler during their trips to see him play at New Castle High this spring.

Nevertheless, the Sox were impressed with Ball’s size (6-foot-6) and the development of a curveball to complement his fastball and changeup. Sawdaye heard talk about Ball flirting with a knuckleball, but never saw him use the trick pitch in a game situation.

“Very rarely do you see a (high school) kid showcase three pitches, and that’s what Trey did,” Sawdaye said. “All in all, he does project to have three plus-pitches, a guy that obviously has to improve in some areas but who we see as a top-of-the-rotation starter.”

The Sox have until July 15 to sign Ball, who also has a scholarship from the University of Texas. He would join a stable of top pitching prospects that includes Allen Webster, Rubby De La Rosa and Brandon Workman at Triple A, Anthony Ranaudo and Matt Barnes in Double A and lefty Henry Owens at Single-A Salem.

“This is a guy whose athleticism and upside would not make him available deeper into the first round in any draft, we don’t believe,” Cherington said. “It just so happened that when we picked at No. 7, he was the top player remaining on our board.”