Wolf, 37, adds depth to an Arizona rotation that ranks 29th in the majors with a 6.57 ERA. Only the Minnesota Twins' rotation, with a 6.89 ERA, has been worse.
The D-backs' staff took a major hit in spring training when Patrick Corbin, a 2013 National League All-Star, was lost for the season after Tommy John surgery on his left elbow.
He won a spot in the Seattle Mariners' rotation out of spring training. But he asked for his release and went back on the market in late March rather than agree to a clause that would have allowed the Mariners to release him in the first 45 days of the season without having to pay his entire salary.