IRVING, Texas -- It's good to be a defensive tackle these days.

It's especially good for Tyrone Crawford.

The Dallas Cowboys locked up their defensive tackle to a five-year extension worth $45.67 million on Saturday afternoon, paying him a $10 million signing bonus and fully guaranteeing him $17.425 million with the likelihood he will be guaranteed $25 million in the first three years of the deal.

There have been a number of reactions on Twitter to the signing: those praising the Cowboys, those praising Crawford, those praising both and those wondering why the Cowboys did not use the money spent on Crawford to keep DeMarco Murray.

The Cowboys were wise to lock up Crawford before his contract year started. Crawford was wise to cash in now because of the unknown. But what about the running back part of the equation?

Well, the position matters.

The Cowboys put a value on the running back position, not the name.

If Murray played defensive tackle, they would have kept him, but the Cowboys made the decision not to pay a running back. It had little to do with Murray. The Cowboys loved him. They wanted to keep him. In a perfect world, they keep him and his 1,845 yards and they sign Crawford and they add Greg Hardy and they sign Dez Bryant and they have the draft they had.

But it's not a perfect world.

The Cowboys valued a defensive tackle over a running back because in their view the defensive tackle is more important. And more difficult to find. They believe they can find a running back a lot easier than they can find a defensive tackle. And they are right. The Cowboys should be able to run the ball fine this year, even if they don't run for 2,354 as a team. The chances they ran for that many had they kept Murray were slim as well.

There are fewer people roaming this world built to do the things Crawford can do compared to what Murray can do. There's a reason why defensive tackles go so high in the first round and running backs don't these days.

Crawford does not turn 26 until November. The Cowboys are going a little on potential here. He has just three sacks in his first three seasons, but he found a home last season in Rod Marinelli's scheme.

In addition to the three sacks, he had 29 quarterback pressures. He had 37 tackles, a low number because Marinelli hands out tackles like manhole covers. Crawford had two tackles for loss. He knocked down a pass and he forced a fumble. In his rookie year, the Cowboys played a 3-4 and he was a defensive end. He missed his second season with a torn Achilles. He returned last year and flourished.

And the Cowboys are banking -- literally -- he will be even better in 2015 in part because they have better pieces around Crawford to help turn those pressures into sacks.

"I don't think we're necessarily betting on upside," executive vice president Stephen Jones said Friday before Crawford's deal was completed. "We just want him to keep playing and playing the way he plays."

It pays to be a defensive tackle.