With Will Middlebrooks out for the rest of the 2012 season thanks to a broken wrist, the question posed in the headline can be answered with, "Boston's new third baseman." Or, at least, one of the options. But who is this 27-year-old infielder?
Valencia was a 19th-round selection in the 2006 draft, with the Twins picking him out of the University of Miami. Unsurprisingly -- but always nice for a pick as late as Valencia -- the 21-year-old performed well against Rookie League competition for 48 games to close out 2006.
From there, it was a standard produce, promote career trajectory for Valencia. He spent 66 games in Low-A in 2007, posting a walk rate over 10 percent and an 874 OPS. He would finish up 2007 at High-A, posting less impressive rates, but would rebound in the first half of 2008 to get himself that promotion to Double-A. He would move into the Twins' top 10 prospects via Baseball America for his performance, coming in at #5:
Valencia's bat speed ranks among the best in the organization. He has good hand-eye coordination and can turn on good fastballs and drive them out of the park. He's strong enough to hit for power from pole to pole. He has improved his pitch recognition and can punish hanging breaking balls. He's a good athlete with first-step quickness and an above-average arm at third base. Consistency, in terms of concentration and execution, would propel Valencia from average to plus defensively. He'd also benefit from more patience at the plate. He rubs some teammates and club officials the wrong way with bouts of immaturity, including taking bad at-bats with him into the field and showing up umpires. He has below-average speed but isn't a liability on the bases.
There's some obvious good there, but it ends on a bit of a sour note. Overall, though, you'd take a prospect with the talents listed, even if he were a bit immature, in the hopes that everything would develop for him, both physically and mentally, by the time he needed to be in the majors.
Valencia had a strong 2009, although his patience suffered in Triple-A, and he was rated the #6 prospect heading into 2010. That season would be his first in the majors, with the 25-year-old playing in 85 games and picking up 322 plate appearances as the Minnesota third baseman. He hit .311/.351/.448, good for a 119 OPS+. Not quite a huge impact bat, but you'd certainly take that.
There were concerns, though, noticeable even at the time. Valencia had a .351 batting average on balls in play, and while he often posted lofty BABIP in the minors, it was occasionally sporadic. Not so much that you would expect him to crater in 2011, but enough that no one should have been expecting another .350 season.
All Valencia has done is fall apart since then, though, and, after a strong start, he's now just a career .259/.300/.392 hitter. The power isn't awful for a middle infielder or third baseman, but when combined with the low average and on-base, it's just not enough. The right-handed Valencia has had issues with same-handed pitching, managing just a 633 OPS (and .268 BABIP) against them, while lefties have been the source of his production: he's hit .318/.363/.472 against southpaws in 311 plate appearances.
Valencia still doesn't have an overabundance of patience, as he's seen just 3.7 pitches per plate appearance in his career, and owns a 5.9 percent walk rate. He doesn't have the plate coverage of the man he's replacing, either, so he hasn't been able to get away with the lack of walks in the same way.
Valencia wasn't supposed to be in the majors with the Red Sox, at least not until September when rosters expand. There's a reason for that, as his career numbers suggest. Against lefties, though, he could be a useful piece in the last month-plus of 2012. Just don't expect a whole lot more than that: if he leans closer to his prospect potential than the career he's actually had, consider it a gift from Red Sox scouting.