The Orioles have added some rotation depth by signing former Oakland Athletic Justin Duchscherer to a one year contract that could pay him a max of $4.5 M in salary ($1.1 M base if he makes the roster) and incentives (based on making a whole bunch of starts, which is quite a longshot). The 33 year-old right-hander hasn't been healthy for a couple years, so this is more an upside signing than one to add veteran stability. Duke has made only 5 major league starts since 2008, which was his first year as a starting pitcher (moving from the pen, which makes looking at his career numbers somewhat deceiving).
In that 2008 season he pitched 141.2 effective innings (2.54 ERA, 3.69 FIP, 4.22 xFIP), based largely on good control (2.2 BB/9). The nice thing about Duke is that his main flaw - inability to stay healthy - isn't a big drawback. The Orioles already had enough guys to slot into the rotation; the issue was more one of quality depth. Pitchers get hurt - there's very little chance of the O's getting through the season with only 5 or 6 starters - and so being able to slot in a guy who has a chance to be an average starter for a little bit and then having some young replacements (Tillman, for example) to step in if (when*) he goes on the DL is nice.
On the mound, Duke doesn't have knock-out stuff. He won't be touching even 90 mph often (if ever), but he'll hit his spots with the fastball and work in a big curve and a sharp slider pretty often.
If Duke does his thing* next year - strikes out a decent (but below average) number of hitters, doesn't walk many, do an OK job of keeping the ball in the yard (which will be tougher moving from Oakland to Baltimore) - then an ERA around 4.50 doesn't seem crazy. I doubt he'll pitch all that many innings - definitely wouldn't expect more than 100 - but 50 of them would give the O's a solid return on investment since he'd probably only be getting ~$1.5 M in that case while providing something like a half a win. That's a half win of pure improvement though, since he's probably taking those 50 innings from whoever's 8th or 9th on the depth chart (and I have no idea who that is, but I'm sure he's replacement level at best). I like the move, and if Duke magically stays healthy (and effective) for the first three months then I could see the O's being able to deal him for a prospect while not harming their plans at all (since I imagine they'd want to get a couple young guys some innings at that point anyway).
* Which is actually not too different from what Koji would give you as a starter. Seems like a decent comparison, especially with the extra added hope of seeing him on the field.
Stats: ERA, FIP, xFIP, K/9, BB/9, WAR