Karstens, 30, became a free agent after being non-tendered by the Pirates in November. He made $3.1 million last season and likely would‘ve gotten about $4 million this year if he had gone through arbitration.
The Pirates were ready to give free-agent lefty Francisco Liriano a two-year, $12.75 million contract to fill Karstens‘ rotation spot, but the deal fell apart after Liriano injured his right arm in late December.
Karstens missed significant parts of the 2012 season with injuries to his shoulder, hip and groin that limited him to 15 starts and 90 2/3 innings. When able to pitch, however, he was effective -- posting an ERA of 3.97. He is the only member of the 2011-12 rotations to have a sub-4.00 ERA each season, having pitched to a 3.38 in 2011.