A year ago, Jacoby Ellsbury’s raw defensive skills were obvious. Yet they just as obviously required refinement.

The outfielder’s blazing speed permitted him to get to balls that might elude others, but the Red Sox still felt that he was learning how to react to the strength of major-league hitters. His routes to the ball were, at times, indirect, and the Sox viewed him as a player who would benefit from further familiarity with the league.

Fast forward to recent weeks, when Ellsbury has seemed capable, at times, of covering the entire outfield expanse by himself. He slammed into a chain-link fence in Toronto to deny an extra-base hit. He made a succession of sliding catches in Yankee Stadium last week.

Against the White Sox over the weekend, Ellsbury was playing center when he raced back and laid out to haul in Orlando Cabrera’s Triangle-bound liner. In left field on Tuesday, he sprinted towards the foul line and made a leaping catch against the grandstand of a Kevin Millar fly ball.

On Wednesday, he completed his tour of Fenway’s nooks and crannies as a right fielder. Ellsbury glided back to the warning track and made a leaping grab before smacking into the wall in front of the visitor’s bullpen to rob Baltimore’s Aubrey Huff of a homer in the top of the fifth inning.

“These past three or four games, his big plays in the field have made a big difference,” said Sox starter Daisuke Matsuzaka.

Third-base coach and outfield instructor DeMarlo Hale suggested that Ellsbury’s progress from 2007 to now has been substantial. His routes on balls both from the corner outfield positions and from center, Hale suggested, have improved, and the 24-year-old has shown spectacular closing speed that has permitted him to emerge as an elite ball tracker.

“He’s improved. I’m very happy with what I’ve seen,” said Hale. “He’s got a knack to go catch the baseball. It’s like a wide receiver finding a way to get under a bomb and get his hands on it.”

Of course, the excitement of Ellsbury’s game also comes with certain risks. He has been throwing himself around the field with abandon. His American League-leading 44 steals and his willingness to bounce into walls and turf alike in the outfield come with a physical toll that the rookie will have to learn to manage.

“That’s part of his competitive nature. He’s going to be the kind of guy who dives, who slides on stolen bases,” said Hale. “He’s going to have to take care of himself. You go through the season and there will be bumps and bruises along the way for him.”

PACKING THEM IN

The Red Sox tied the Major League record for consecutive home sellouts, packing Fenway Park for the 455th straight game, a run that dates to May 15, 2003. The Sox matched the standard that was set by the Cleveland Indians from June 12, 1995 to April 2, 2001.

“I’ve not seen anything but sellouts since I’ve been here. Think about that,” marveled Sox manager Terry Francona, who has been with the club since 2004. “That’s unbelievable. It’s the norm. And I hope, when I say it’s the norm, I’m hoping it’ll never get to the point where we take it for granted.

“We have a great situation here. We have the best ballpark, as far as atmosphere, that there is. The owners have made the amenities better for the fans. We’re very fortunate.”

THE TRAINER’S ROOM

First baseman Kevin Youkilis missed his second straight game due to back spasms. The Red Sox are hopeful that, with an off-day on Thursday, he might be ready to return to the lineup by the time the team plays the Rangers in Arlington, Texas, on Friday.

If that happens, Youkilis will be part of a rather impressive group of corner infield reinforcements. Both Mike Lowell (oblique) and Sean Casey (neck) appear poised to return from the disabled list in time to play against Texas. J.D. Drew’s lower back strain, however, has produced less obvious progress.

KOTSAY CATCHES ON

With Youkilis out, Mark Kotsay made his 29th career appearance at first base, and his first since 2006. Francona suggested that Kotsay’s actions as a first baseman are good, a notion that was demonstrated when Kotsay completed an unusual double play on a Luke Scott grounder to end the eighth.

With a runner on first, Kotsay fielded Scott’s grounder, stepped on first and then fired cleanly to second base. Because the Red Sox were in a shift against the pull-happy Scott, it was third baseman Jed Lowrie who covered second base and tagged out Oscar Salazar.

Francona felt far fewer reservations about featuring Kotsay at first than he did in 2004, when he asked first baseman Doug Mientkiewicz to start at second base.

“That was outside of the box,” recalled Francona. “My heart was in my throat that night.”

Kotsay also contributed a huge game-tying triple in the bottom of the eighth, and now has six extra-base hits (five doubles and a triple) in six games with the Sox.

PITCHING IN

Though Daisuke Matsuzaka (16-2) did not factor in the decision, the Red Sox improved their record to 21-4 in games that he has started. Matsuzaka, who allowed four runs (three earned) in six innings, is unbeaten in his last seven starts, going 5-0 with a 2.46 ERA in that span…

Justin Masterson, who entered with the Sox trailing 4-2, won for the first time as a reliever, contributing two perfect innings in which he whiffed a pair. When the Sox tied the game in the eighth, they had Jonathan Papelbon warming prior to the ninth, but opted to stick with Masterson for a second inning.

“I think that tells you what we think of Masterson right there,” said Francona.

Alex Speier is a Senior Writer for WEEI.com.