PHILADELPHIA -- It must be tough to be a running back. No matter how many yards you gain, everyone thinks they could do better.

Last season, DeMarco Murray rushed for 1,845 yards on 392 carries for the Dallas Cowboys. Murray led the NFL in both categories. So naturally, his backup was underwhelmed.

"He had a good year last year," Cowboys running back Joseph Randle told reporters Wednesday, "and I got to sit back and watch a lot and I felt like there was a lot of meat left on the bone."

That was sort of the same message that coach Chip Kelly sent when he released LeSean McCoy, who led the NFL in rushing in 2013. McCoy ran for 2,926 yards in his two seasons playing for Kelly. He became the Eagles' all-time leading rusher last season at the age of 26.

And yet, Kelly traded McCoy to Buffalo for linebacker Kiko Alonso, citing McCoy's $13 million salary-cap hit as the reason. But Eagles owner Jeff Lurie shed a bit more light on the move, saying that Kelly prefers more of a "downhill" running back. McCoy's style makes him a little slower to get to a hole than Murray, and sometimes McCoy would get trapped in the backfield.

But let's face it. McCoy gained 1,607 yards in 2013 behind a healthy, effective offensive line. His numbers dropped a bit in 2014 -- 1,319 yards on roughly the same number of carries -- but the Eagles' offensive line was plagued by injuries. If you have a good back running behind a good line, your running game will work just fine.

Clearly, though, coaches and teammates are like fans when it comes to watching a running back at work. The holes look bigger and the running lanes look clearer when you're watching on TV or in the film room.