According to Jon Heyman on Twitter. Sanchez is coming off a miserable 1-9, 8.07 season split between the Royals and the Rockies. As recently as 2010, he went 13-9, 3.07, and he pitched passably in 2009 and 2011. He's remarkably similar to Francisco Liriano, with whom the Pirates have been trying unsuccessfully to finalize an agreement. Both are lefties with above average stuff and serious control problems. Also, neither is a Gary Sheffield client. Sanchez has a career K/9 of 9.1, although it plummeted to 6.3 last year. He also has walked five per nine innings in his career.
It remains to be seen whether this will be a major league or minor league deal. It also remains to be seen what effect such a signing would have on the Pirates' interest in Liriano. Sanchez is clearly a project and couldn't be counted on to be in the rotation at the start of the season.
UPDATE 9:49 PM by Charlie: Rob Biertempfel says the Pirates are in fact nearing a deal with Sanchez, and that it will be a minor-league contract, in which case it's really nothing to be concerned about. There was, in my opinion, zero chance of anyone signing Sanchez to a major-league deal after his implosion last season. Sanchez is a nice arm with a bit of upside, and nothing more. Personally, I doubt this has much to do with Liriano -- he and Sanchez are very similar, as WTM notes, but they're similar in about the same way Red Robin and White Castle are. If you're in the mood for Red Robin and it's too crowded, you'd probably consider going any number of other places, including places that don't serve burgers, before you headed to White Castle, where you only go if it's three in the morning and you're inebriated and desperate.
UPDATE 2/5, 3:25 PM by WTM: Tom Singer is tweeting that Neil Huntington has told him the Pirates want to sign both Sanchez and Liriano, that it's not either/or. As we know from Singer's reporting on Liriano, you can take that to the bank . . . .