There's been a bit of hand-wringing over the Pirates' lack of interest in Mazzaro this year, since he got good results for the Pirates in 2013 and continued to post nice ERAs with Indianapolis this season. In spite of that, the Pirates outrighted him twice this year, which means that nobody had interest in taking him off the Bucs' hands. His peripherals have been unimpressive, and while he isn't exactly a soft-tosser, his velocity this season was a bit below average for a righty, given that it's now routine for righty relievers to throw in the mid-90s.
The Pirates acquired McGuiness from the Rangers for reliever Miles Mikolas last December, back when they lacked many better lefty first base options. McGuiness then didn't even beat out Travis Ishikawa for a roster spot, and he languished in Indianapolis until he was designated for assignment a few weeks ago. He's a competent Triple-A hitter, but he isn't likely to be much more than that.