As per Jon Paul Morosi of MLB Buzz.
Rich Harden represents one of several high-risk, high-reward arms on the market, alongside Justin Duchscherer, Ben Sheets, and Brandon Webb. Each has shown flashes of ace-level potential, yet none have done a great deal over the past two years - in fact, the four have combined for only 384.1 IP over the last two seasons. I suppose it's worth noting that Rich Harden has been the most durable (and I use that term very loosely) of the bunch, tossing 233 IP over that time. Those innings haven't been very good, mind you, as Harden's posted a 5.33 FIP, 4.70 xFIP, and 1.91 K/BB, while allowing about flyballs on roughly 47% of balls in play.
Morosi suggests that teams may be looking at Harden as a reliever, as his excellent stuff would profile quite well in shorter, maximum-effort stints. While this is certainly true, I disagree with Morosi's notion that it could mitigate Harden's injury risk, as well - in fact, I disagree with that sentiment as a whole. As a reliever, Harden would throw significantly fewer pitches per outing. At the same time, however, he'd be throwing more frequently with less rest, and putting more effort into each and every pitch. It seems counter intuitive, in my mind. That doesn't mean it isn't worth a shot, as a team could leverage its risk a great deal by moving Harden to the bullpen - but I don't see it as a certainty.
That being said, Harden is only 29, and his numbers could improve a fair bit from a move away from Arlington. Despite my better judgment, I am somewhat intrigued by the possibility of him in the bullpen, as well. I think a pitcher of his caliber is worth a risk for the Yankees, as a team that can absorb a monetary mistake, but I wouldn't be comfortable with Harden (or Duchscherer, Sheets, or Webb) being handed a rotation spot.