The Vikings placed Cassel and Fusco on injured reserve Wednesday. Both players were hurt Sunday at New Orleans.
"You work so hard in the off-season to give yourself an opportunity to go out there and play, and then to have it happen this early in the season, especially with the belief that I have in this team, the thoughts of going on and having a lot of success this year, and for it to happen this early is super devastating to me," Cassel said.
"At the same time, now all your focus goes into your rehab and getting better and trying to get back on the field."
Teams have the option of placing one player on injured reserve with the intent to bring him back to practice after six weeks and to play in games after eight, but they saved that designation for now.
Cassel was replaced by rookie Teddy Bridgewater, and Christian Ponder will be the backup moving forward. Vladimir Ducasse filled in for Fusco.
Coach Mike Zimmer said the team considered using that designation for tight end Kyle Rudolph, who had surgery to repair a sports hernia on Tuesday.
But the initial prognosis after surgery is a little more promising and Zimmer said the team believes Rudolph could be ready to go sooner than the eight weeks he would be required if he was on injured reserve.
"We're anticipating that it's not going to be that long," Zimmer said.
Quarterback McLeod Bethel-Thompson and tight end Ryan Otten were signed to the practice squad. Tight end Chase Ford and offensive lineman Austin Wentworth were elevated from the practice squad to the active roster.
Linebacker Chad Greenway also played in New Orleans with a broken left hand and aggravated a rib injury during the game. His status for this Sunday against Atlanta is uncertain, meaning the Vikings could be without five starters from their lineup in the season opener.
Running back Adrian Peterson remains on paid leave while a child abuse charge against him in Texas is pending.
Cassel was re-signed to start in front of Bridgewater, and now the first-round draft pick from Louisville has had his development accelerated. The 32-year-old Cassel completed 41 of 71 passes for three touchdowns and four interceptions and 425 yards in three games.
"I think Teddy will do a tremendous job for us and hopefully I can help him in a mentoring position and be able to help guide him and bring him along," Cassel said.
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