How bad is Jason Witten's injury, really?

In Adam Schefter I trust. All others must show MRI results. In his latest mailbagInsider, Adam discusses the Dallas Cowboys' concern over the severity of tight end Jason Witten's spleen injury, and he doesn't offer Cowboys fans any warm, comforting thoughts about it:

The Cowboys don't know the extent of the injury right now, which suggests that they should be worried. They're going to have to wait another week or so to determine whether he needs surgery. Right now, the Cowboys are of the mind that Witten will not need surgery. But if something changes, and he does, he would be sidelined indefinitely.

I stand by what I wrote on this the other day: There is no possible way for the Cowboys to replace Witten. They can talk all they want about John Phillips' development, and Phillips may well be a good player and an acceptable tight end. But it's a long way from "good player and acceptable tight end" to Witten and what he means to Tony Romo and the Cowboys' offense. With the offensive line a wreck, Miles Austin's hamstring hurt and Dez Bryant not under 24-hour surveillance, the Cowboys have very little on which they can rely on offense. Witten's reliability is the most valuable thing about him.

The Cowboys are not strong or deep in enough areas to weather the long-term absence of one of their star skill-position players. A serious injury to Witten or Austin or Bryant or DeMarco Murray or especially Romo would cripple whatever chances they have of contending in the NFC this season. For that reason they need to make sure and do the right thing by Witten in the short term. If they were to rush him back or do anything that might jeopardize a complete recovery and require surgery, they would be dooming their season. Fortunately for them and for Witten, it appears they are being very careful.