OXNARD, Calif. -- There are typically only four or five players an NFL team can't afford to lose.

For the Cowboys, Jason Witten is in that top five.

Todd Archer and Ed Werder are reporting that Witten suffered an injury to his spleen in the first quarter of the preseason opener at Oakland on Monday night. Witten's status for the season opener at the New York Giants on Sept. 5 is in question.

Forget about the rest of the preseason; the Cowboys can't afford to play without Tony Romo's favorite receiver when it counts.

Yes, Romo does have Dez Bryant and Miles Austin. But Romo's safety net has always been Witten.

He doesn't catch a lot of touchdown passes (five in 2011), but he gets the offense going, evident by his 47 receiving first downs. Only Bryant (48) had more on the team.

On third- and fourth-down plays, Witten had 17 first-down receptions; Bryant led the team with 20.

The Cowboys' chances of winning are diminished with Witten's availability in doubt.

So who stands behind Witten?

John Phillips, an above-average blocker with some good receiving skills, is nursing an ankle sprain and is close to returning to practice. Phillips has just 22 career receptions and returned to action last season after suffering a torn ACL in his right knee in 2010.

In the draft, the Cowboys selected James Hanna, who is more of a pass catcher than a blocker. His time with tight ends coach John Garrett will be monitored more this week because he'll get the start in San Diego on Saturday night. Hanna's biggest issue is a lack of consistency.

After the 3-0 victory against Oakland, coach Jason Garrett talked about a next-man-up philosophy as something he's preached to the Cowboys.

With Witten out -- for the team's sake, hopefully just until the regular-season opener -- somebody will fill the void, be it Hanna, Phillips or Andrew Szczerba.

If not, the Cowboys will have some problems.

This isn't losing the fullback, or some backup guard. You're losing a franchise tight end. A player who will receive Hall of Fame consideration at the end of his career.

It's not the end of the world, but if you don't have Witten for the Giants game, it will feel that way.