IRVING, Texas (AP) -- Already 0-2 without injured stars Tony Romo and Dez Bryant, Dallas must move on without the versatility of running back Lance Dunbar because of a season-ending knee injury.

Next up: undefeated Super Bowl champion New England, followed by the surging New York Giants and Seattle. The only relief is the bye next week, after Tom Brady and the Patriots (3-0) make their first visit to the $1.2 billion home of the Cowboys on Sunday.

So after a 26-20 loss to New Orleans on Drew Brees' 80-yard touchdown pass to C.J. Spiller on the second play of overtime, the Cowboys (2-2) were left with the disappointment of a missed chance as they try to find ways to win until Romo returns from his broken left collarbone -- at least five more games.

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"That's never really been an issue for us as a team," coach Jason Garrett said Monday. "Somehow, some way we come back the next week regardless of what the result was and you get ready for the next challenge. That's what we believe in around here."

Garrett said Dunbar appeared to have a torn anterior cruciate ligament in his left knee, an injury sustained when he was returning the second-half kickoff against the Saints. An MRI was to determine the extent of the damage, followed by a plan for surgery.

The fourth-year player had 54 yards rushing at halftime, second most of his career. The only other time he had more -- 82 yards against Oakland on Thanksgiving 2013 -- he sustained another season-ending left knee injury.

Before his season high in rushing, he was leading NFL running backs in receiving yards and was tied in catches.

"To say we have someone in-house who is going to do those same kinds of things, I don't know that we have somebody like that," Garrett said. "But we have guys in-house who can do different things and hopefully we'll play to those strengths."

Bryant, who has missed the past three games with a broken right foot, is likely to return before Romo, perhaps by the end of the month.

Dallas lost cornerback Orlando Scandrick to a season-ending knee injury in training camp, and linebacker Sean Lee left the New Orleans game with a concussion after going into the game as the NFL's leading tackler.

"That's what happens in this league," 13th-year tight end Jason Witten said. "You've got to be able to regroup. We have lost our fair share, but this team doesn't make excuses. We'll get back at it."

Receiver Brice Butler, who came in a trade to add depth after Bryant's injury, is sidelined by a hamstring problem. And backup linebacker Andrew Gachkar has a foot injury that triggered the game-winning sequence for the Saints when he left the game and Spiller beat his replacement, rookie Damien Wilson, up the sideline on the next play.

"I don't think there was confusion," Garrett said. "I think everyone knew what the coverage was and what we wanted to do on that and the key is getting lined up and handling it the right way once the ball is snapped. Obviously we didn't get that done."

There are reinforcements coming with the end of four-game suspensions for linebacker Rolando McClain (substance abuse) and defensive end Greg Hardy (domestic violence).

Garrett said both are expected to practice this week, and the team cleared roster space by waiving defensive tackle Ken Bishop and linebacker Keith Smith.

But the Cowboys are still one step closer to an "oh-fer" without Romo, as executive vice president of personnel Stephen Jones put it last week when admitting that Dallas would be out of contention at 2-7 in that scenario.

With a modest goal of a 4-5 record when Romo is eligible to return, the Cowboys would have needed just one more win if they could have taken advantage of backup quarterback Brandon Weeden's tying touchdown pass to Terrance Williams late in regulation.

Instead, the defense let the Saints easily get into field-goal range in the final 1:51 without a timeout. After a reprieve when Zach Hocker missed a 30-yarder in the final seconds, Brees delivered the winner to Spiller.

"The guys that we're asking to step up, they shouldn't be as good as the ones they're replacing," owner Jerry Jones said. "But they're playing hard and competing and I'm proud of that."