most sites list Shelden as strictly a PF or F but that is mainly because of his 6'9" height and drafting of Al Horford (1" taller). Shelden last year played both F and C.

HoopsHype has him in the depth chart as a PF but his profile lists him as a C

so while the current roster should slot him as a F he is definitely eligible to play C (kind of a mike dunleavy/danny granger situation - being depth charted in the SG role)