Just look at the list of veterans who joined the Sox organization during the 2005 championship season, but didn't make it to Chicago: Tony Alvarez, Roosevelt Brown, Jim Bullinger, Trace Coquilllette, Brad Fullmer, Jeremy Giambi, Wilton Guerrero, Ricky Gutierrez, Bobby Jones, Felix Martinez, Greg Norton, and Robert Person. Even Bullinger, who last pitched in the majors 7 years earlier, had people freaking out because they thought he was part of KW's master plan for the first place Sox.
Signings like this happen every year. I like having people with MLB experience as Sox pennant race injury contingency plans. For a minor league team like the Knights, even a Doug Davis might draw a few more fans and help the team advance to the post-season. It probably won't hurt the youngsters to have a teammate who lasted 13 years in the majors, had some good years, overcame cancer, and pitched in the playoffs.