Dan Haren of the Athletics may also be on the Red Sox’ radar screen.

AP / Jeff Chiu

BOSTON — On the eve of the start of the winter meetings, the intrigue surrounding Minnesota Twins left-hander Johan Santana took one more unexpected turn.

The Red Sox yesterday did an about-face and decided to include outfielder Jacoby Ellsbury in a package for the premier pitcher. Previously, the Red Sox had declared both Ellsbury and pitching prospect Clay Buchholz off-limits in trade talks.

That, however, was before the New York Yankees — the Red Sox’ chief rival on the field and in these negotiations — reluctantly agreed to include top pitching prospect Phillip Hughes in their offer to the Twins.

Over the last few days, the feeling had been that the Sox were merely continuing their negotiating for Santana in an effort to further drive the price up for the Yankees. But Boston’s reported move to include Ellsbury in the deal casts the Sox’ strategy in a new light.

That tactic led some associated with the Yankees to express concern yesterday that the Red Sox were nearing an agreement for Santana.

The decision to include Ellsbury in their offer, however, also resulted in the Sox removing lefty Jon Lester from their previous package of players. Initially, the Sox had offered the Twins Lester, Coco Crisp, infield prospect Jed Lowrie and an unspecified minor-leaguer.

The addition of Ellsbury probably means that Crisp is out, since the Twins would have no use for two center fielders.

The Yankees’ latest offer is said to include Hughes and outfielder Melky Cabrera. The Twins have been pushing for the Yanks to also include Ian Kennedy in the package, and the Sox’ upgraded offer may give them leverage there to extract more from New York.

For their part, the Yankees have refused to part with both Hughes and Kennedy and have told the Twins that a third player in the deal cannot come from the team’s remaining elite crop — Kennedy included.

Santana, who has a full-no trade clause and intends to wield it to land a six-year contract extension from any team striking a deal for him, told the Twins that he would veto a trade to any team except the Yankees or Red Sox. He also warned them that he would not accept a deal in-season, forcing the Twins to move him this week or lose him to free agency after the 2008 season, when his current contract expires.

Even as the Sox monitor the Santana talks, they remain interested in at least two other starters said to be available at the meetings.

Oakland’s Dan Haren, whose acquisition cost would be nearly that of Santana but who is under contract for another three years at $15.4 million — just slightly more than Santana’s $13.5 million for 2008 — is one target.

Yesterday, indications surfaced that the Sox have also had discussions with the Milwaukee Brewers regarding Ben Sheets. Sheets, 29, was 12-5 with a 3.82 ERA for the Brewers last year and has won in double figures in six of his seven seasons in the big leagues, but due to injuries hasn’t made more than 24 starts in any of the last three seasons.

Beyond attempting to bolster an already-deep starting rotation, the Red Sox’ agenda in Nashville is expected to be relatively minor.

If Crisp isn’t part of a deal for a front-of-the-rotation starter, he could be moved to obtain catching help. Jason Varitek has just one year remaining on his contract and the Sox would like to upgrade the backup spot, which has been manned by Doug Mirabelli — a free agent — for the last five years.

The team must also fill in around the margins, needing a backup first baseman to replace free-agent Eric Hinske.

Should the Sox not retain free-agent outfielder Bobby Kielty, they would need to find a fourth outfielder, preferably one who can hit right-handed to help spell the left-handed-hitting J.D. Drew in right. In the event that both Crisp and Ellsbury stay, of course, that search would be called off.

smcadam@projo.com