The Washington Nationals agreed to terms with pitcher Dan Haren on a one-year, $13 million contract. It’s one of those rare cases where we shouldn’t assume the deal is entirely done yet.

The reason Haren could be had on a one-year deal is the same one that will make his pending physical more than routine: He’s got a history — and a recent history — of back and hip problems. Haren missed three weeks last season with a hip injury. He also posted his worst numbers since breaking in with the Cardinals in 2003 and 2004, putting up a 4.33 ERA, 4.24 FIP, and a career-high home-run rate of 1.4 homers per nine innings.

In possibly related news, Haren’s fastball has dropped 2 mph in the past two seasons, and now tops out in the high-80s. If that’s a temporary issue related to a temporary and treatable injury, then the pitcher with the third-best strikeout-to-walk rate in baseball over the past half-decade becomes a royal steal on a one-year deal, with his numbers likely to improve significantly in the lower-offense environment of the National League. But there’s a certain wisdom of crowds efficient market dynamic in play here. If last month’s rumored Haren deal with the Cubs fell through, and if all the pitching-starved teams in baseball decided that a 32-year-old Dan Haren wasn’t worth as much as, say, Jeremy Guthrie, there’s probably some real risk in play here.

The good news for the Nats is their existing pitching strength and depth gives them all kinds of options. With Stephen Strasburg, Gio Gonzalez, Jordan Zimmermann, and Ross Detwiler on board, they don’t need Haren to pitch anywhere near the ace level he’s shown in the past, and they have quality pitching to cover for a DL stint, should one occur. Haren’s arrival also means the Nats are probably out on Zack Greinke or a blockbuster starting pitcher deal with a team like the Rays. Instead, they can focus on bolstering their bullpen, with Mike Morse their most attractive trade chip.

And since we’re fans of the arcane on Team Grantland, Haren is one of the best-hitting pitchers in baseball with a career .223 average. If Strasburg’s early returns are any indication (.277/.333/.426 in a 53-plate appearance sample in 2012), the Nats could put up more of a fight at the bottom of the order than any other NL club.

More from the Winter Meetings:
• The Hot News From the Winter Meetings (12/4)

• For Some Reason, the Giants Think Angel Pagan Is Worth $40 Million (12/3)

• Red Sox Make Their First Move With Napoli Signing (12/3)

• Who will make the biggest splash? (12/3)