Optimism for the Minnesota Vikings season peaked Sunday in the team’s first game at U.S. Bank Stadium, a preseason outing before the largest crowd in the team’s home history. Quarterback Teddy Bridgewater led the team quickly down field for a two-minute-drill touchdown to end the first half, then exited to roars from the crowd, his day done.

“Nothing to worry about,” coach Mike Zimmer said afterward.

He spoke too soon.

On Tuesday, Bridgewater suffered a serious injury to his left knee at the team’s practice and is almost certainly sidelined for the season.

The official diagnosis: a complete tear of the anterior cruciate ligament (ACL) in his left knee, as well as other structural damage. Surgery is pending, and the team said “recovery time will be significant.”

The third-year quarterback was felled without being hit. Trainers surrounded him, practice was quickly canceled and an ambulance was called — a rarity in the NFL — to take Bridgewater to a hospital.

Zimmer’s voice quavered as he spoke following the injury, saying: “He’s a great kid. Let’s let him get healthy and get taken care of. … I love this kid. Our fans love this kid.”

Bridgewater, the charismatic 23-year-old, and Zimmer, the old-school coach, have been tied together since each joined the Vikings in 2014. The Vikings won the NFC North with an 11-5 record in 2015 and seem poised to take the next step — with Bridgewater’s development being the major reason. He has had two promising seasons and was even a Pro Bowl replacement player last season.

The team’s season ended last year with a shocking, subzero loss to Seattle in a playoff game at its temporary home, TCF Bank Stadium on the University of Minnesota campus. But the spring thaw fostered high hopes — the words “Super Bowl” were being whispered by fans who, in the team’s 55-year history, have seen the Vikings lose that game four times and fail to get there on other occasions where the stars seemed to align.

With running back Adrian Peterson, who led the NFL in rushing last season, joining Bridgewater to lead the offense and Zimmer’s fanatic attention to detail certainly making a strong defense even better, projections from around the country were positive. Every game at the new stadium in downtown Minneapolis is sold out, with the Sept. 18 regular-season home opener against the Green Bay Packers sure to be among the most-hyped events in team history.

Now some dreams are fading, with veteran backup quarterback Shaun Hill taking over as the team explores its options at the most important position.

“No one is going to feel sorry for us,” Zimmer said, “so I’m not going to feel sorry for us, either. I’m not going to let this team feel sorry for itself. We’re going to grieve today and [be] upset about it. It’s more about our feelings for Teddy and him as a person and getting better than it is about anything else.”