Which RB should i start?

I have 3 good running backs, Chris Johnson (Ten), Willie Parker (Pit), and Clinton Portis (Was), im thinking Parker and Johnson because parker is healthy and is facing the albert hansworthless titans, and portis is facing the giants who have justin tuck, osi umenyiora, and antonio pierce... clinton is my boy but he didnt to great against the giants last year, what do you think