His contract only guaranteed him $500,000 or 1/5th of his pay.
Wow. I wasn't aware of this, and agree with your conclusion.
But Arizona is a great place to land....
Is that really about the landing spot or what the contract tells us about his skills/health/attitude or what the NFL thinks about his skills/health/attitude? If he landed on the Niners (a fairly middle of the road landing spot) with a similar contract, would it have been better? I would argue no. The Giants, definite no. After some time has past since the signing, I am now in the camp (if there is one) that the landing in Arizona is neither patently good nor bad (after previously leaning towards bad following the aftermath of the Denver letdown) and that we are all just guessing at this point.
He landed on a bad offense. But, he has a coach that knows him and that appears to be giving him a chance to start where another team may not have. He still has fairly weak and fragile competition for the starting job. Off hand, I'd say that the competition at RB is the most important factor right now for Mendenhall.
On the other hand, he is getting paid far from starter salary. It is also conceivable he could get cut in camp if he doesn't show good health and performance or if Ryan Williams shows good health and performance.
Not knowing (i) what Arians is/was thinking, (ii) what Mendenhall was thinking, (iii) how healthy Mendenhall is or Ryan Williams will be and (iii) how bad Arizona will actually be this year, I am of the opinion that we won't really know what kind of landing spot this is until we get into camp and into the season. In this case, performance will likely matter, but not in the way most think (i.e., great performance does not indicate a great landing spot necessarily and poor performance does not indicate a bad one necessarily). A combination of factors will determine how the landing spot plays out.
For example:
If he performs lights out in camp, shows good skills, easily takes the job but can't get going in the season due to the poor offense, than Arizona will have proven to be a poor or at best a "not great" landing spot. He would have won the job in a number of other teams with better offenses in that case.
If he is mediocre in camp, wins the job anyway (either in camp or during the season) due to Ryan Williams' equally mediocre performance and/or poor health and puts up RB2, even RB3 type numbers, I'd consider Arizona to have been a great or at worst a "not bad" landing spot. On any other team, he could have been fantasy irrelevant.
If he is awesome throughout camp and into the season despite a poor offense, then that may tell us very little about the AZ landing spot (because he probably would have lit it up in other teams as well) and with that kind of performance, who really cares?
Similarly, if he sucks in camp and can't win the starting job, then that would tell us little as well as he would have similarly sucked in any situation, whether Arizona or Denver. And again, who cares about landing spot if he sucks that bad.
There's a lot of grey area we could fall in as well depending on performance.
Bottomline, its a wait and see on this one imo.
As for Ryan Williams as a value play, I don't think he presents any more "buy low" value than does Mendenhall at the moment. I would be inclined to pay a 2nd for Williams right now as a gamble. I would pay the same for Mendenhall as well. Something tells me though that I won't be getting either for that price.