After 51 days of physicals, negotiations, and a reworking of his contract, the signing of first-baseman/catcher Mike Napoli is officially official. The Red Sox made the announcement today, placing Napoli on the 40-man roster and designating reliever Chris Carpenter (Theo Epstein’s compensation) for assignment. Napoli was introduced via a conference call to writers this afternoon, and cleared up a few unanswered questions.

Rumors had been swirling throughout the last month or so about Napoli’s physical, the results of which appeared to be holding up the finalization of what was then a three-year, $39 million deal. Today, we learned that Napoli has avascular necrosis (AVN), in both his hips. The disease causes deterioration of bones because of an interruption of blood supply to the bone, and is common primarily in the shoulders, knees, and hips. It’s the same disease that ended the career of baseball and football star Bo Jackson, though Ben Cherington assures that the two cases are different ^[1]. Napoli believes he’s been playing with the condition for at least the last season, though he was surprised by the diagnosis.

Upon researching the disease a bit, the most common treatment for those who suffer from AVN in their hips is a total hip replacement or other surgeries, but Napoli says he’s taking medication and is performing all baseball activities without any restrictions ^[2]. The cause of the AVN is not known at this time, and hadn’t been apparent ^[3] in Napoli’s March 2012 MRI. The disease was caught early and it seems the prognosis for 2013 is good ^[4]. The discovery of the condition accounts for the shortening of the deal to one year and $5 million (plus performance bonuses) since the disease is degenerative. This likely means that Napoli will be limited to first base exclusively, unless there are no other options behind the plate on a given day.

In other, far less significant news, Napoli won’t be wearing the #25 that he donned in Texas. Instead he’s switching over to #12, left unclaimed after Ryan Sweeney was non-tendered. His former number was also available, but Napoli wanted to go with the number he wore growing up. ^[5]

Now Boston’s next priority should be securing a solid back-up at first, preferably a defensive-minded, left-handed hitting 1B. There are a few trade candidates (Smoak and Carp from Seattle) and choices on the free agent market (Kotchman, Overbay), but with Napoli’s health a concern going forward, the Sox would benefit from having a capable and reliable back-up plan.