MANKATO — When the Minnesota Vikings’ first-team offense took the field on the opening day of training camp, Matt Cassel stood behind center.

However, first-year head coach Mike Zimmer said the position was far from solidified Friday after the camp’s first walk-through at Minnesota State University, Mankato.

“It doesn’t mean that when we play the St. Louis Rams (to start the regular season) he’s going to be the starter, but he’s going to line up with the first team,” Zimmer said about Cassel. “He’s the No. 1 quarterback, but he’s not declared the starter.”

Cassel — in his 10th NFL season — will challenge last year’s starter, Christian Ponder, and rookie first-round pick, Teddy Bridgewater, for the starting role.

“I know that I’m going to go out here and work every day. Those guys are going to push me, and that’s just part of this process,” Cassel said. “I think it makes us all better — the competition.”

Despite having more than twice as much professional experience as Ponder and Bridgewater combined, the fact that Cassel is absorbing offensive coordinator Norv Turner’s playbook is making the race tighter.

“I’m trying to learn an offense just like they are,” Cassel said. “Each and every day, my focus is on that. You can’t be afraid to make mistakes because we’re all going to do it, especially this time of year. You’ve got to make those corrections.”

According to Cassel, camp has been going well for Bridgewater.

“He’s quiet for a rookie, which is always a good thing. He got me a Gatorade today, which I was really thankful for,” Cassel said with a laugh. “He’s worked hard, and I’ve been very impressed with his work ethic and how he’s picked up the offense. We’ve had a great relationship. The same goes for myself and Christian (Ponder) as well.”

Bridgewater was the 32nd overall selection — the last pick of the first round — of the 2014 NFL draft. Zimmer felt he was a good value at that spot. News outlets including the Star Tribune, the New York Daily News and Fox News used the phrase “Tanking For Teddy” in articles about the Cleveland Browns’ strategy when they traded starting running back Trent Richardson. The theory was that the Browns would intentionally lose all their games to get the No. 1 pick to draft Bridgewater.

“Teddy’s been a really good get for us,” Zimmer said. “I’m ecstatic to have him. I love his personality. The Vikings’ fans will be proud to have Teddy Bridgewater here for a long, long time.”

As a sophomore, Bridgewater led Louisville to a 33-23 win over Florida in the Sugar Bowl. He completed 20-of-32 passes for 266 yards with two touchdowns and an interception against the Gators, a team that was ranked No. 5 in total defense, according to the Associated Press. His junior year, he piloted the Cardinals to a 12-1 record. The only blemish was against Central Florida, a team that dropped 52 points on Baylor and won the Orange Bowl.

Ponder will look to improve on last season’s numbers. He completed 152-of-239 passes for 1,648 yards with seven touchdowns and nine interceptions. His passer efficiency rating of 77.9 was 28th in the league.

Cassel’s numbers were slightly better, and he played in all five of Minnesota’s wins. His rating was 25th in the league at 81.6. Cassel completed 153-of-254 passes for 1,807 yards with 11 touchdowns and nine interceptions.

Minnesota has three quarterbacks on its roster. However, the Vikings picked up Kain Colter as an undrafted free agent. Colter is listed as a wide receiver, but he had success as a quarterback in college at Northwestern. His 2,180 career rushing yards are the most by a quarterback in Wildcat history, and his pass efficiency rating of 139.0 was second on Northwestern’s all-time list.

Zimmer is the ninth head coach in Vikings history. This year will be his 21st season as an NFL coach, and he spent the last 14 seasons as a defensive coordinator. The workload this season has been an adjustment.

“The only difficult thing for me as the head coach right now — as opposed to being the defensive coordinator — I was evaluating 45 guys, and now I’m evaluating 90,” Zimmer said. “It’s more volume for me.”