Well his name is pronounced "terry-o", doesn't really fit w chariot but whatever.
The Cubs got burned by a rookie middle infielder in Cedeno last year and really wanted a proven MLB player at basically every position. Murton is the least proven starter and as you know they got Floyd in case Murton flops in his sophomore year.
Theriot will get his starts but unless there is an injury, he won't be an everyday guy this year IMO.
As for his #'s last year, truth is he faced a lot of crappy pitchers as teams made a habit of plugging in weak SP when possible against the Cubs once August came around instead of wasting a top guy's outing.
As for Derosa, I'm leery too, but as I understand it, he altered his swing coming into last year and that may explain the jump in #'s.