Washington is a converted WR and pass catching is his strength, but Riddick isn't going anywhere. Washington is not a between the tackles rusher so will not fill that role which is currently vacated. Howard has all the opportunity to take over the 3 down gig ROS. He is also a more talented and polished runner.
Howard graded by some as the "best pure runner RB" in this class. Washington is not polished in his vision, ball security or leverage/power and this is probably because he is a converted WR. The fact that he is a converted WR makes you think that is a plus in PPR and it would be under normal conditions. The problem is DET already has a great 3rd down pass catching RB, so he is not going to be filling that role (he wasn't out there in their last hurry up drive vs GB). Some miscast him as a goal line, short yardage or early down back because of his size, but his vision/feel is not even average, let alone good (known for running into his blockers), neither is his footwork or his power/leverage in short space movement. He is not known for running between the tackles, more of an outside bouncer, electric guy in space. He takes long strides more closely resembling a WR. I just watched his tape from last week and he never hit any holes or would be tacklers with low pads, sapping a lot of his potential power/leverage he could have generated with his size. I counted several times where he was actually thrown backwards at the end of plays, leaving him open to fumbles/injury (other known problems).
Add to this that Washington has had durability concerns. The only thing you can say he has an advantage over Howard is his offense is better, but that doesn't mean the RB opportunities are necessarily better. Let's look at who CHI has faced so far. Are they really as bad as people are saying? In spite of the "horrid" offense, Langford has scored two goal line TDs for CHI this year. Langford isn't even a good short yardage back (Howard is much better), so there is some indication that the line had something to do with the scores. I confirmed this with the tape. This was against HOU and PHI, which are both tough rush defenses that shut down KC/PIT offenses where the "pedestrian" Langford actually outscored Ware vs HOU. We all saw what PHI did to PIT’s running game last week, holding them to 3 points. Williams had 8 rushes for 21 yards. Is CHI really that bad or did they just have two tough games vs tough D to start the season? Langford and Howard were both running effectively vs DAL.
Who has DET faced? IND (horrible), TEN (meh) & GB shut down their running game last week. I only see marginally better RB opportunities in DET under the best circumstances, and much worse opportunity under the most likely circumstances. Going with Washington over Howard you are banking on Riddick going away, and even if he did, its doubtful Washington could carry the load by himself so Zenner would come into the picture as the between the tackles, short yardage guy and Washington would be the pass catching, dynamic guy. Howard is a more talented/effective/polished runner in a better situation. I realize his page count is only 4 and this one is on page 20. That's fine, but based on opps and talent, Howard's ceiling and floor is definitely higher now and most likely into the future if he proves himself as the best back on the team over the next month.