A pup tent could accommodate the people remaining in the camp of Cardinals running back Rashard Mendenhall, and even then there would be room for coach Bruce Arians and his Kangol caps. It’s not often a running back rushes for 154 yards in his first start and then is benched the next game. Yet, that’s what happened to rookie Andre Ellington last Sunday when Mendenhall returned from a toe injury to start against the Texans. Not only did Mendenhall start, he touched the ball (13 rushes, one reception) one more time than Ellington (11 rushes, two receptions), despite Ellington’s emergence as a more dangerous offensive threat. Asked Monday about the division of labor at running back, Arians said, “I think it’s right where it needs to be.” It’s an interesting point of view, because Arians said this off-season he’s not a believer in running back by committee. He wanted versatile backs, not specialty guys to fill niches, he said. The situation he faces now, however, is that Ellington is the best back the Cardinals have, and it’s not close. To continue to divide the workload equally between Ellington and Mendenhall is stubborn at best and foolish at worst. In a typical game, there will be at least 30 or so “touches” to distribute among the running backs. The game plan should be for Ellington to get at least 18 of them, with the rest of the work going to Mendenhall and Stepfan Taylor. (Ryan Williams is out of this conversation because it appears the only way he will be activated is if two of the other four backs are injured.) Ellington has gained more yards than Mendenhall (388 to 323) on slightly more than half the carries (54 to 105). His yards per carry (7.2) is more than double that of Mendenhall (3.1). Remove Ellington’s 80-yard run against the Falcons, and his average is still far greater (5.8) than Mendenhall’s. Arians’ concern about overworking Ellington has been justifiable, and the debate has a chicken-or-egg element. Is Arians holding Ellington back? Or has the limited workload kept Ellington fresh and explosive? It’s a legitimate argument and good reason not to make Ellington into a workhorse such as Jamaal Charles, Adrian Peterson or Marshawn Lynch. At least not this season. Those three each average more than 20 rushing attempts and receptions a game. This is not a call for Mendenhall to be deactivated. There is still a substantial role for him to play on Sundays, and despite his fumble in the final minutes last Sunday, Mendenhall showed he can help this offense.