We definitely needed that extra pitcher once ERod went down. It was clear within the first week or so that he wouldn't be ready for the season opener. Considering all of the other question marks in the rotation, that was the time to make a deal. They definitely lucked into Wright's performance.
If they had not picked up Buchholz's option, they could have grabbed a more reliable starter for similar or less money (i.e. JA Happ, Doug Fister, Colby Lewis) and the rotation would be looking much better.