BOSTON — Every year, players chosen in baseball’s annual first-year Player Draft reach the big leagues sooner and sooner.

Three players chosen in 2005, less than three years ago, have already played prominent roles in the big leagues for the Red Sox — outfielder Jacoby Ellsbury, who leads the American League in stolen bases; pitcher Clay Buchholz, who has already pitched a no-hitter, and Craig Hansen, who become a bullpen mainstay.

Further, Justin Masterson, last night’s starting pitcher against Tampa Bay, was chosen in the 2006 draft.

But despite the immediate impact these players have had in a relatively short period of time, the team’s philosophy hasn’t deviated. When tomorrow’s draft takes place, the Red Sox will still be guided by the same principle: select the best player available, regardless of need.

“For us,” said general manager Theo Epstein yesterday, “drafting where we’re drafting (30th overall, last in the first round), we’re looking at players who need time in the minor leagues (to continue their development). It’s a really, really rare case where you can factor in (drafting for a specific) position.”

Toward that end, it wouldn’t be terribly surprising if the Sox tomorrow chose a pitcher, despite the inventory of talented young arms in their minor league system. Still, around baseball, the one player the Sox are said to be focusing on is shortstop Reese Havens out of the University of South Carolina. Havens, an all-SEC selection in 2006, is an infielder by trade, but there has been talk within the organization of drafting him with the purpose of converting him into a catcher.

On days like tomorrow, the Sox are victims of their own success. By virtue of compiling the game’s best won-loss record in 2007 and their World Series title, the Sox select last in the first round.

In 2007, the team forfeited its first-round pick by signing free agent shortstop Julio Lugo. In 2006, the team didn’t pick until the 27th slot. In fact, the last time the club had a selection in the first 20 players, the Sox picked David Murphy, now with the Texas Rangers.

The team’s resources have allowed the Sox to take some chances in the draft. In 2005, Hansen was pegged as a top-10 talent but slid toward the end of the round, in no small part because he was represented by Scott Boras and was demanding a major league contract.

The Red Sox gave Hansen a $4.4-million deal and he was pitching for the Sox less than three months later.

But Epstein argued yesterday that the team has not often gone after players whose signability has been a factor, especially in the early rounds.

“What makes a good draft,” he said, “is hitting on players in the top rounds. The 2005 draft (when the Sox got Ellsbury, Buchholz, Hansen, along with Jed Lowrie and Michael Bowden) is kind of the model for us.”

Occasionally, the Red Sox have gambled in later rounds. In the same 2005 that spawned Ellsbury, Buchholz, et al, the Sox drafted a high school player out of the Bronx in the 14th round. But the young player, the New York high school player of the year, was intent on going to college and elected to attend Vanderbilt, rather than toil in the minors.

Tomorrow, it’s expected that that player, Pedro Alvarez, will be among the top five players chosen.

“That’s kind of a double-edge sword,” said Epstein. “On the one hand, we’re proud we were able to identify talent like that. On the other, you kind of kick yourself for not being able to sign him. But in the end, the way you have to look at it, the most important thing is to be on the right guys.”

Beyond their own first-round pick at No. 30, the Sox will also get a compensation pick at 45 for having lost Eric Gagne to the Milwaukee Brewers.

smcadam@projo.com