Center fielder Jacoby Ellsbury left Friday's game with an injured right shoulder. (AP)

The Red Sox could be forgiven if they are holding their breath while awaiting the diagnosis of injured center fielder and leadoff hitter Jacoby Ellsbury. After all, the team’s blueprint for contention is largely dependent upon a core of elite players.

In discussing why he felt comfortable focusing on the addition of complementary pieces rather than superstars this offseason (for this article), Sox GM Ben Cherington suggested the following:

“We had three guys in the top 10 of MVP voting last year. I don’t think there are many teams that had three guys in the top 10 of MVP voting that don’t make the playoffs,” said Cherington. “So from a roster construction standpoint, we did feel we needed to add some things to make the roster function better, but we didn’t feel we needed to add a superstar.”

Of course, if Ellsbury is sidelined for a significant length of time based on the right shoulder injury he incurred on a hard slide into second base in the bottom of the fourth inning, that equation changes. It was difficult not to recall the rib injury that Ellsbury suffered in the sixth game of the 2010 season, in which he took a knee to the chest from Adrian Beltre and was, for all practical purposes, lost for the rest of the year.

This injury might not be as severe as that non-displaced fracture of five ribs — Ellsbury was being sent for further evaluation — but certainly, the possibility of a shoulder injury that forced last year’s runner-up in the AL MVP race to leave the field while holding his arm pinned to his side suggests the possibility that the Sox will have to be without one of their cornerstone players.

Any injury to a regular would be bad for the Sox, but the potential loss of Ellsbury would damage the team at a position where it is arguably thinnest. With Carl Crawford not yet playing in rehab games in his return from wrist surgery, the team had been featuring a starting outfield of Ellsbury and two players (Ryan Sweeney and Cody Ross) whose career numbers suggest that they are best suited for platoon roles, with Sweeney playing against righties and Ross against lefties. Likewise, fourth outfielder Darnell McDonald — who would likely enter the starting lineup if Ellsbury is unavailable — has significant career platoon splits that suggest he is best suited for duty primarily against lefties.

The only other outfielder on the Red Sox’ 40-man roster (aside from Crawford, on the DL, and Ryan Kalish, who is on the 60-day disabled list) is Che-Hsuan Lin, a tremendous defender but one who has yet to show an ability to handle Triple-A pitching (he’s hit .230/.322/.296/.618 in 91 Triple-A games this year and last).

Among players in Triple-A who are not on the 40-man roster, Jason Repko made an extremely favorable impression in spring training. He’s 4-for-8 so far for Pawtucket, but like Ross and McDonald, he’s right-handed.

Pedro Ciriaco was something of a revelation in spring training, though he’s played just eight games in the outfield in his eight pro seasons. He’s off to a nice start in Pawtucket, hitting .333 with a .391 OBP. He, too, is a right-handed hitter.

Daniel Nava (.333/.474/.533) has the best numbers thus far of any of the Pawtucket outfielders, and of course he received his first career big league opportunity in the wake of Ellsbury’s 2010 rib injury. He’s a switch-hitter, though one with decidedly better splits as a right-handed hitter than a lefty.

Nate Spears is an organizational favorite who spent a brief spell in the majors last year. He, like Ciriaco, offers the team versatility, and he’s a left-handed bat who might better complement McDonald and Ross than the aforementioned right-handed hitters.

Finally, there is a bit of a wild card in Lars Anderson, who played outfield in the regular season for the first time just a couple of days ago. Anderson is left-handed and on the 40-man roster, so in some ways, he represents an interesting fit, though there would have to be something of a leap of faith for the Sox to feel that, given his limited experience in the outfield, he could offer them depth.

In other words, there are no ready-made prospects who would be a perfect fit in the absence of Ellsbury. There is no Ryan Lavarnway or Will Middlebrooks equivalent of a top prospect who could come in and be a candidate for everyday duty. That being the case, barring a trade or unexpected signing (amazing that Johnny Damon was a free agent until Thursday), the Sox would appear most likely to face the prospect of an outfield featuring McDonald (who, like Nava, got his Red Sox break thanks to Ellsbury’s injury in 2010), Ross and Sweeney, with a less-than-ideal candidate from the minors to round out the group.

In other words, the obvious truth is that the Red Sox have to keep their fingers crossed that the injury to Ellsbury was not severe, and that his absence will not test the team in an area where their talent is thinnest.