Success of Boston's Outfield Rides on Jacoby Ellsbury's Transition to Left Replacing Jason Bay is going to be no easy task for the Red Sox. Replacing his 36 home runs and 119 RBIs with a 25-year-old who hit eight home runs and notched 60 RBIs in 2009 is, however, exactly what the Red Sox are doing — but not because Jacoby Ellsbury’s offense can go toe-to-toe with Bay’s.

Instead, Boston is confident that Ellsbury will be just fine as Bay’s replacement in left field because of the same thing that got him noticed in the majors in the first place: his speed and his defense.

It’s no secret that the outfield at Fenway Park can be a challenging place to make yourself look good — just ask Manny Ramirez or Johnny Damon for confirmation on that — but since making his big league debut in 2007, Ellsbury has executed to near perfection, boasting a fielding percentage of .997 in parts of three major league seasons.

Will that success translate from center field to left field? It will have to if the Red Sox want GM Theo Epstein’s defense-first plan to pan out in 2010.

The offseason signing of veteran Mike Cameron presented Boston with a tough call: Should they move Cameron to left field after he spent the majority of his 15 big league seasons manning center, or should they pull the switcheroo on a young outfielder who’s had just over two years of big league experience but has shown tremendous speed and instincts in the outfield?

Boston chose the latter — for good reason — and if the plan works, Epstein and the Red Sox will look very, very good. If the plan works, the Red Sox will boast what has the potential to be one of the best outfields in the league.

And it all starts with Ellsbury. (And ends with J.D. Drew staying on the field.)

Despite the fact that he has been best suited to center for the majority of his Red Sox career, left field is not uncharted territory for Ellsbury. Before spending 100 percent of his time in center in 2009, Ellsbury essentially split time between center (66 games) and left (58 games) in 2008. In those 58 games, Ellsbury boasted a perfect fielding percentage. In fact, Ellsbury did not make an error at all until 2009, when he registered two in 153 games in center field.

Bay’s defense was as solid as it comes — he didn’t commit an error in 150 games last year — but given Ellsbury’s experience and his age, his line isn’t too shabby.

Of course, there are perks to switching from center to left. Ellsbury will get the opportunity to throw out some runners — something that former Red Sox Fred Lynn thinks Ellsbury’s speed will help him succeed at — and he may even be able to rest his legs a little and therefore improve his offense.

"I hope it works out like that," Ellsbury told ESPN.com earlier this month. "It's hard to say because I haven't played a full season [in left field], so ask me at the end of the year how my legs feel. It would be nice if it did save my legs for the offense. A lot of the best base-stealers over the years have been corner guys, so there may be something to that. I'm not sure, but hopefully, because it'll be nice to save my legs a little bit."

Switching positions is never easy, especially in Ellsbury’s case; he felt like he proved himself in his first two-plus seasons in Boston, only to get booted when a veteran free agent came to town. The move isn’t permanent — and according to ESPN, the team has stressed that it is not a demotion — but still, the change will take some getting used to.

It’s a challenge Ellsbury isn’t worried about fulfilling.

"I felt comfortable,” Ellsbury told ESPN of his previous experience in left. "[Playing left at Fenway is] something that's a little bit different; it's unique than any other ballpark. I think it will be a smooth transition, but at the same time they've said I'll play a little center field, too."

Ellsbury, of course, is confident that it is a transition he can handle. But just in case he runs into some trouble, he has one of the best left fielders in the history of baseball to take pointers from.

"I talk to Jim [Rice] all the time, but I haven't talked to him about that," Ellsbury told the Web site. "I'm sure I will talk to him while we're [at spring training]. We kind of joke around more about golf and who can drive it farther."

Can Ellsbury’s offense replace Bay’s? Maybe someday. But can his defense replace Bay’s? Absolutely.

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From now until Opening Day, NESN.com will run down 25
things
that need to happen for the Red Sox to win the World Series.

March
17: Play .500 ball or better on the road.