Alex Wilson at LeLacheur Park in Lowell, shortly before starting his pro career in 2009. (Alex Katz)

The Red Sox added six players — right-handed starters Allen Webster and Steven Wright, reliever Alex Wilson, catchers Christian Vazquez and Dan Butler and outfielder Alex Hassan – to their 40-man roster in order to protect them from the Rule 5 draft. A brief look at the group:

• Webster, arguably the top prospect whom the Sox got from the Dodgers in the August blockbuster, had a 3.86 ERA and 129 strikeouts (along with 61 walks) in 130 2/3 innings, with the sinkerballer permitting just two homers all year while pitching for the Double-A affiliates of the Dodgers and Sox. He’s considered a high-ceiling pitcher with front-of-the-rotation potential if he can command his arsenal more consistently.
• Wilson, a second round pick out of Texas A&M in 2009, was converted to the bullpen in 2012. He spent the entire season in Triple-A Pawtucket, forging a 3.72 ERA, striking out 78 and walking 33 in 72 2/3 innings. His mid-90s fastball and slider are viewed as potential late-inning weapons out of the bullpen.
• Vazquez, 22, is considered perhaps the Sox’ best defensive catching prospect, and though he’s spent just 20 games playing above A-ball (he was promoted late in the season to Double-A Portland), he’s shown both a decent approach and some power potential. The Sox could have left him unprotected and risked losing him in the Rule 5 draft, but given the paucity of solid catching prospects, they considered the risk too great to expose him to that process.
• Butler, 26, represents a catching depth option for the Sox. He gets high marks for his defense, game management and leadership, and he’s shown enough offense (.259/.357/.417/.774 in four minor league seasons) since the Sox signed him in 2009 as an undrafted free agent that the team felt there was a chance of losing him if it did not add him to the 40-man roster.
• Wright, 28, became a knuckleballer in 2011. He enjoyed a terrific 2012 campaign, albeit one that featured high walks totals (4.4 per nine innings), going 10-7 with a 2.54 ERA, 119 strikeouts and 69 walks in 141 2/3 innings and permitting just nine homers. The Sox acquired him from the Indians at the trade deadline in exchange for first baseman Lars Anderson; after one start with Double-A Portland, he finished the year with four starts in Triple-A, where he had a 3.15 ERA in 20 innings. Wright gives the Sox potential starting depth; the right-hander still has three minor-league options, meaning that he offers long-term rotation depth for the team.
• Hassan is perhaps the biggest surprise of the group. The 24-year-old hit .256/.377/.365/.743 in Triple-A this year. A two-way player in college at Duke who was originally drafted as a pitcher but convinced the Sox to develop him as an outfielder with a strong showing in the Cape League after being taken in the 20th round of the 2009 draft, Hassan has one of the most advanced plate approaches of anyone in the Sox system. Though he’s shown limited power for now, the Sox believe that the corner outfielder has a chance to develop into some power later in his career (much as Kevin Youkilis did).

To clear the space for that half-dozen, the Sox removed five players from their 40-man roster, designating Ivan De Jesus Jr., Danny Valencia, David Carpenter, Sandy Rosario and Zach Stewart for assignment. All five were added in 2012 from outside the organization, four through trades, one via a waiver claim.

A quick look at that group:

• Stewart, acquired from the White Sox in the Kevin Youkilis trade in June, allowed 14 runs in 5 2/3 innings in two disastrous big league starts for the Sox.
• Carpenter, whom the Blue Jays sent to the Sox for Mike Aviles as part of the compensation agreement for manager John Farrell, is 1-5 with a 5.70 ERA, 60 strikeouts and 29 walks in 60 big league innings.
• Valencia, a third baseman, hit .188/.199/.299/.497 with just three walks in 161 plate appearances with the Twins and, following an August trade (for Rookie Level outfielder Jeremias Pineda) Red Sox, a performance that resulted in him spending most of the year in the minors.
• Rosario, claimed off of waivers following the season, has given up 13 runs in 7 2/3 innings in the big leagues, but he showed a three-pitch mix (93-97 mph fastball and an inconsistent but interesting slider and changeup that flash plus potential) that suggest the potential for a quality middle reliever. In Triple-A this year, he had a 1.04 ERA, 24 strikeouts and zero unintentional walks in 26 innings.
• De Jesus was acquired from the Dodgers in the August blockbuster. As an out-of-options utility infielder, he seemed likely to be behind Pedro Ciriaco on the depth chart, and so became a roster casualty.

Two of the Red Sox’ decisions qualified as mild surprises.

First, the inclusion of Hassan on the list of protected players was unexpected, though in retrospect, perhaps it shouldn’t have come as too great a surprise. In a world where players capable of posting reliably high on-base percentages are becoming increasingly rare commodities, Hassan’s ability to post a .377 OBP in Triple-A in what qualified as a down year suggested that the Sox might risk losing him if he was exposed to the Rule 5.

After all, there are currently just FIVE free agents who had at least 200 plate appearances in 2012 with an OBP of .350 or higher — Jonny Gomes, Jeff Keppinger, Nick Swisher, Josh Hamilton and Bobby Abreu. In his four minor league seasons, he has a career .391 OBP, and the Sox thought highly enough of him to make him one of their only drafted-and-developed non-roster invitees to big league spring training camp in 2012. Meanwhile, his .377 OBP in 2012 — again, a career-worst in a full season for the 24-year-old, who has moved up a level a year — can be matched among big league free agents only by Gomes, who also posted a .377 mark this year.

Secondly, the omission of Josh Fields came as something of a surprise given his outstanding performance in Double-A and Triple-A this year. But, with a 40-man roster that’s already overcrowded with relievers, the Sox opted to roll the dice in hopes that they will be able to keep Fields as non-roster minor league depth. Fields enjoyed a breakthrough with his command this year, dominating in a year-end spell in Pawtucket (19 strikeouts, 2 walks, 0.00 ERA in 13 2/3 innings) to put himself back on the prospect radar. Still, it is fair to wonder whether his breakthrough in his age 26 season (Fields turned 27 in August) is sustainable, particularly given his struggles in the Dominican Winter League, allowing eight runs in six innings while punching out eight and walking seven — something that might diminish the likelihood of a club investing a roster spot in him through the Rule 5 draft. At the least, the performance inconsistency between the regular season and winter league underscores that it might be difficult for a team to carry Fields on its 25-man big league roster for a full season.