Coach Jason Garrett said Wednesday the move to Cassel was an attempt to spark a team that needs to win at least once, and probably twice, in the next four games without Romo, who will be out at least that long because of a broken left collarbone.
"We just felt like we wanted to give Matt an opportunity to be in this role and see if we can get our offense going a little bit more and get our team going a little bit more," Garrett said.
Cassel made 71 starts for New England, Kansas City and Minnesota and has 33 wins to just five for Weeden.
In their 30-6 loss to New England on Sunday, the Cowboys went without a touchdown for the first time since an 18-16 win over Washington in 2011.
Also, rookie guard La'el Collins will replace Ron Leary at left guard.
Durant (elbow) and Person (ankle) were both ruled out after missing a short week of practice for the Falcons (5-0). Durant will be missing his second straight game.
James Stone gets his first start of the season at center, always a crucial position for the visiting team in the raucous Superdome.
Star receiver Julio Jones is expected to play despite lingering hamstring and toe issues.
Heyward tweeted Wednesday that the league penalized him for writing "Iron Head" on his eye black during a game. Heyward's father, Craig, spent a decade as a running back in the NFL and went by the nickname "Ironhead" for his physical style of play. Craig Heyward died in 2006 at 39 after a lengthy battle with cancer.
Heyward tweeted "Got fined for honoring my Dad who bravely fought cancer on my eye black."
"It's just sad that I got fined for honoring a man I respect and love," Heyward said. "I'm not trying to go outside the NFL rules. I'm just trying to draw attention to the disease that took my father's life."
Though Buffalo Bills starting quarterback Tyrod Taylor has a sprained left knee, Coach Rex Ryan won't entirely rule him out from playing against Cincinnati on Sunday. Ryan said Taylor would practice on a limited basis, with backup EJ Manuel taking a majority of the snaps. ... Andrew Luck is starting to look like his old self after missing the last two games with a sore right throwing shoulder. The Indianapolis Colts quarterback was dressed in pads and participated in all of the throwing drills during the early portion of Wednesday's practice, which is open to the media. The Colts hope to have Luck back for Sunday night's showdown against New England. ... Ben Roethlisberger took a small step toward returning to action. The veteran Pittsburgh Steelers quarterback (sprained medial collateral ligament) was a limited participant in practice Wednesday, taking part in non-contact seven-on-seven passing drills. ... New England Patriots offensive lineman Nate Solder was placed on season-ending injured reserve, three days after he left a game against Dallas with an arm injury. ... Oakland Raiders Coach Jack Del Rio says an MRI on defensive end Justin Tuck's shoulder, injured Sunday, is "not good" but would not speculate if the injury could lead to Tuck's being placed on injured reserve. Tuck has one sack and seven tackles through five games. ... The Arizona Cardinals have placed safety Chris Clemons (hamstring) on injured reserve and elevated cornerback Cariel Brooks from the practice squad. Clemons injured a hamstring in Arizona's 42-17 victory over the Lions in Detroit last Sunday. He is the second player Arizona player to go on injured reserve this week. On Tuesday, the team placed inside linebacker Kenny Demens on IR with a torn anterior cruciate ligament.