McCoy is an elite back, and typically very healthy. There are probably two other guys in his tier, and personally I think you don't trade them away. I understand most people say that the RB position is devalued these days. Not so for the upper echelon game changing guys like AD, Lynch, and McCoy.
If it was me I personally wouldn't have traded for Alonso, especially when you flipped McCoy into 3 guys who McCoy happens to have more healthy seasons than all three combined. I also think McCoy is more talented then possibly all three of them.
I understand you spread the risk out with additional cheaper RBs. That's smart, but the same thing could have been achieved with the squad you had and supplementing it with late round RBs if you truly feel the RB position is devalued.
In reality only one guy can have the ball at a time, and I want the most talented guy of the group (and reliable) to get those touches. McCoy was that guy. Murray and Matthews might be able to the do same thing, but they'll cost just as much as McCoy does now. So you got three injury riddled less talented players (judging by the past), for minimal cap relief (judging by the newly established contracts), with the upside of spreading some risk out at the RB (which could have been done anyways).
Personally, that's a net loss in my mind. If you asked me if I could have McCoy or Murray and Matthews in the backfield I'd take McCoy everyday. Sweeten the deal with Alonso and I think I'd stay put especially with a guy coming off an ACL.
Like I said before, I could be proven completely wrong this season but that's just my opinion on it.
If you want to extend the life of your RB, then you don't give him all of those touches. Sure, Murray was run into the ground last season, but he still has 600 fewer carries than McCoy in his career and they are the same age. If you know McCoy, then you know he isn't the RB you want in the game on 3rd and short, or anywhere near the red zone. His touches were given to Chris Polk in the RZ near the end of last season because McCoy just couldn't get it done (Polk had 3 rushing TDs in the last 3 weeks of the season). Is he talented? Yes, but you're fooling yourself if you are putting him in the same category as Lynch and AP. A top tier RB can get you those yards on 3rd and short when you need them most
*. Instead, we're subbing him out or just passing the ball. McCoy is a highlight reel, he'll give you those 3-4 runs you see on ESPN, but you're missing the other 15+ carries where's his getting stuffed and missing holes because he's dancing around in the backfield trying to hit homeruns with positive yards are there for the taking.
Maybe it's because you aren't an Eagle fan, but McCoy looked like he lost a step last season. He was nowhere near as explosive as he was in 2013, and at times even had defenders catch up to him where seasons prior he would take runs to the house. Maybe it was some undisclosed injury that was nagging him last season (some say it was a turf toe), but we don't know. You do not pay a running back 11M+ per while you can't even trust him in short goal line situations. McCoy has had the benefit of working with two great offensive minded coaches in his career, so it'll be interesting to see Murray's progression now that he has a better coach in Philly.
Looking at Murray, he's only missed two games the last 2 years, it's not like he's some fragile player. He'll be fine as long as we don't run him the same way DAL did last year, which is obviously the plan. That is why Ryan Matthews is here. Having them share the load both extends their playing careers, and keeps them healthy. Sports Science was actually one of the reasons why Matthews was interested in playing for Philly.
In reality, this is a team sport unlike the NBA. We're filling out an entire roster, and there is no point in paying a RB so much money when he isn't even an ideal fit for your offensive system (N/S runner). Chip runs a no huddle up-tempo offense, there are times when McCoy isn't even in the game for an entire series of plays. As much as Philly runs the ball, we're going to need more than 1 capable RB to do it, and when Sproles has much more value as a return man and hybrid WR, you need to find someone else to carry the rock when the starter is getting a rest. We saved about 800K by getting rid of McCoy. In return we got the reigning NFL rushing champ, a good RB to spell Murray when need be (if he stays healthy, but it helps that he won't get as many carries here as he did in SD per game), WT3 (Walter Thurmond III) who is going to challenge Carroll and Boykin for the CB2 job as far as I know, and a potential cornerstone player on defense in Kiko Alonso.
*Lynch may not belong here, it's clear his coach rather have Wilson pass the ball.
The Cowboys can find a foundation back in rounds 1, 2, 3, and maybe even in round 4 of the draft. It is a pretty deep RB class. Eagles didn't take shit.
Murray accounted for almost 2300 yards on offense for Dallas. We definitely took something.