By Scott Garbarini, NFL Editor

(Sports Network) - Though the Dallas Cowboys and San Diego Chargers each had victorious debuts to their 2012 preseasons, both teams came out of their openers with significant casualties that will certainly affect the game plan for their Saturday night clash at Qualcomm Stadium.

The biggest development in Dallas' otherwise-uneventful 3-0 victory at Oakland this past Monday was the serious injury sustained by Cowboys' tight end Jason Witten. The seven-time Pro Bowl selection lacerated his spleen after taking a hard hit from Raiders linebacker Rolando McClain in the first quarter, rendering him out for the rest of the club's exhibition slate and putting his status for the Sept. 5 regular-season opener against the rival New York Giants into question.

Witten, who hasn't sat out a game since his rookie campaign of 2003, is prohibited from partaking in any physical activity for at least another week and could require surgery. His place will be taken by John Phillips in the interim, though the capable reserve just resumed practicing after missing time with an ankle sprain.

San Diego's 21-13 home triumph over the Green Bay Packers was also marred by the loss of running back Ryan Mathews for an extended period. The 1,000-yard rusher fractured his clavicle on his first carry of the night, an injury that will sideline him for the next 4-to-6 weeks.

The Chargers are hopeful that Mathews will be ready to go for their Week 1 matchup at Oakland, but will spend the remainder of the preseason prepping veteran Ronnie Brown and possibly Curtis Brinkley and fullback Le'Ron McClain for potential increased roles.

San Diego is also without starting left tackle Jared Gaither (back) and slot receiver Eddie Royal (groin) at the moment, while defensive lineman Antonio Garay likely won't play in Saturday's tilt after spraining his ankle in a recent practice.

Quarterback Philip Rivers is healthy and is in line for an increase in snaps after working only four possessions in the mistake-filled win over the Packers, in which the two combatants combined for seven turnovers. He ended one of those drives with a 23-yard touchdown pass to tight end Antonio Gates, but was also intercepted once and finished 3-of-5 for 37 yards.

Jarrett Lee took over for the remainder of the contest and completed 15-of-22 throws for 235 yards, including a 36-yard scoring strike to wide receiver Vincent Brown. The undrafted rookie won't see as much time in this weekend's game, however, with No. 2 quarterback Charlie Whitehurst back from a sprained knee that kept him out of the opener.

Brown ended with a game-high 81 yards on four catches, with Brinkley topping all players with 42 rushing yards and a touchdown on 11 carries.

Tony Romo also saw limited action in Dallas' snoozer with the Raiders, with the Cowboys' signal-caller hitting on 3-of-6 attempts for 30 yards on a trio of series. He'll once again be operating without wide receiver Miles Austin, who'll be held out a second straight week with a hamstring strain, and behind an offensive line that again won't have two regulars in center Phil Costa (strained back) and left guard Nate Livings (hamstring).

The Dallas defense was able to pitch a shutout against Oakland despite the absences of valued nose tackle Jay Ratliff (plantar fasciitis), outside linebacker Anthony Spencer (hamstring), end Jason Hatcher (groin) and highly touted rookie cornerback Morris Claiborne (sprained knee). Claiborne, the No. 6 overall pick in April's draft, will suit up for his first outing as a Cowboy this weekend, however, with Hatcher expected back as well.

Dallas has prevailed in seven of the 13 all-time preseason bouts between these teams and came through with a 16-14 win in its last visit to San Diego, which took place in 2010. The Chargers exacted some revenge via a 20-7 triumph at Cowboys Stadium last August, though.