Indeed, when the Pirates non-tendered Karstens in November, it was widely assumed that he would not be returning to the Steel City. Knowledgeable reporters like Dejan Kovacevic (I disagree with a lot of his opinions, but he clearly does his reporting and knows his stuff) assured us that Karstens was a goner, so it was very surprising to see him sign with the Bucs at the reported low rate of $2.5 million for one year.
One has to assume that Karstens was not in the Pirates' offseason plans when they made the decision to non-tender him, especially given the coincidental timing between the Karstens signing and Francisco Liriano's injury complications. But at the same time, it's hard to argue with how things worked out.
Neal Huntington deserves some credit for properly assessing Karstens' value, as he clearly couldn't get close to the $4 to 5 million that he would have earned in arbitration on the open market. The non-tender was almost universally panned by the Pirates community (this author included), but it seems that Huntington knew what he was doing.
Frankly, aside from the initial disappointment at the fact that the Pirates are probably going to lose Liriano, the only other concern is that there is something wrong with Karstens, as there is little other explanation regarding how cheaply the Bucs were able to sign him for.
Karstens has struggled with injuries in recent seasons, but he has been a very consistent starting pitcher otherwise, and 2012 was his best season to date. A slightly improved strikeout rate and always-impeccable control led Karstens to be a well above-average pitcher when he did take the hill last year, compiling 1.7 wins above replacement in only 90 innings pitched.
This type of performance, even given some anticipated regression, is well worth the $2.5 million that the Bucs are said to be paying Karstens. It's worth $5 million too, which is why many were upset at the original decision to non-tender the pitcher.
Karstens remains an injury risk, and he is not someone who the Pirates can just pencil into the rotation for the entire 2013 season. But the Bucs should have some money to throw around, as Karstens will make $4 million less than Liriano would have made this season and is costing Pittsburgh significantly less than anyone expected him to.