BOSTON — At the annual Boston Red Sox rookie program, players usually talk about their hopes of reaching the major leagues. The program, after all, serves as an orientation to the majors for prospects who are close to making it, in the eyes of the organization.

But half of the 10 players who gathered this week in Boston have already made their major league debut.

The Red Sox brought those players to the rookie program because some of them are fairly new to the Boston organization.

“It gives a different flavor,” Boston Player Development Director Ben Crockett said Friday during the program’s media session. “With acquisitions, we have four (or) five guys new to the organization. That has changed the direction (of the rookie program) a little bit.”

There is another reason for the older players. There are not enough new prospects considered major-league ready who have not already gone through the program.

A prospect gap?

“I don’t think so, necessarily,” Crockett said. “I think there’s another group coming up.”

But most of that group will be in Class A ball this season, at Greenville or Salem.

Only one player in the rookie camp this week is expected to be with the Portland Sea Dogs in 2015 – Henry Ramos, an outfielder who shined in Portland last year before a season-ending leg injury after 48 games.

Three of the five players with major league experience – pitchers Edwin Escobar, Heath Hembree and Zeke Spruill – were acquired through trades. Another, outfielder Rusney Castillo, was a touted free agent from Cuba who signed in August ($72.5 million for seven years).

Castillo, 27, played briefly for three minor league teams – including the Sea Dogs – before joining Boston for the last two weeks of the season. He is expected to be the starting center fielder for the Red Sox.

The other experienced outfielder, Mookie Betts, was not invited to last year’s rookie program, but he emerged last season, going from the Portland Sea Dogs to a starting position in the outfield at Fenway.

Betts, 22, could be Boston’s staring right fielder, especially if Shane Victorino is not healthy. Manager John Farrell has talked about Betts being an ideal leadoff batter.

“Whether its leadoff or ninth, I just want to crack the lineup,” Betts said.

Betts began 2014 as part of a prospect-rich Sea Dogs team that saw several players promoted to Triple-A and, in Betts’ case, the majors.

The likelihood of so many promotions in 2015 is much lower. This year’s Portland team is not expected to carry a lot of top prospects, although highly regarded reliever Robby Scott could be on the team if he’s not on Triple-A Pawtucket’s roster.

The four best young prospects who were not in Boston this week include three who might make it to Portland sometimes this season: pitchers Trey Ball, 20, and Teddy Stankiewicz, 21, and outfielder Manuel Margot, 20. All three are expected to begin the year in Salem. Third baseman Rafael Devers, 18, is destined to begin in Greenville.

Boston filled out its rookie camp with four others who played last year in Portland. They did not reach the majors, but are close – pitchers Eduardo Rodriguez (obtained from Baltimore in the Andrew Miller trade) and Brian Johnson, catcher Blake Swihart and infielder Sean Coyle. Swihart is the only one who also took part in last year’s program (the group usually includes one catcher).

Spring training begins next month in Fort Myers, Florida, with pitchers and catchers reporting Feb. 20.