Start Randy Moss, Johnny Knox, or Thomas Jones in my flex week 13?

Please help, last time i played thomas jones against denver he had 4 carries for 6 yds. Moss has been terrible but he does get Kerry Collins id say thats an upgrade..... ANd JOhnny Knox safe play for 6 to 13 pts not much upside. Knox all year has not done anything huge and im fighting for a buy week. Go all out and start Randy Moss??? Or play it safe??? thanks!