Westbrook is for sure the play...
No downside at all against Clev, barring injury.
Williams has been hot and is a great play against Den, but he isn't as much of a sure thing as Westy.
Turner is a stud but a tougher matchup keeps him on your bench.
Bottom line...you are choosing between 3 of the top 7 or so RBs for this week, so any of them could end up on top. But Westbrook has the best chance of that, and little chance of a quiet game.
Good luck