The problem is that Houston doesn't play ST's. Niether does Barlow. Washington will be activated, because of his important role on ST's. The Jets won't activate 4 RB's in any one game. So, two things have to happen. Blaylock will have to be inactive for Houston to suit up. Until Washington gets the CS's confidence that he can replace Blaylock as the CoP third down RB, Houston won't be activated in a game.
If I had my way, Blaylock would be the RB that is inactive, but Mangini seems to want to stick with him in that CoP/3rd down role, and that makes it impossible for Houston to get any playing time.
The Jets O line has shown, even with the two rooks, that it can pass protect well enough, but the run blocking is not good at all so far, and that is an understatement. A cut back runner like Blaylock has no place on the field behind such a poor run blocking O line, while guys like Barlow and Houston can break tackles, and are much better suited to running the ball behind a line that can't create any running lanes.
Not having Kendall healthy hurts the running attack as well.... he's the best run blocker on the O line. Once he and Teague are healthy enough to play, the Jets running attack should improve, but it's a FF waste land even when they do, as far as RB's are concerned. The Jets O line still needs a RT and a RG that can run block, and that isn't going to happen this year.