The Vikings began preparations for Sunday's season opener against the 49ers without Brian Robison after the 11-year veteran was released during this weekend's roster cuts. But if you ask longtime teammate Everson Griffen, he's betting on the 35-year-old Robison returning to the NFL on another team to continue his 12th NFL season — which Robison had said would be his last.

"If I know my dog, White Chocolate, he playing," Griffen said Monday. "I think he's going to play. He was looking good. He was playing good ball."

Coach Mike Zimmer credited Robison for helping to establish the culture he sought when he was hired to coach the Vikings in 2014. Ascension of the players Robison helped mentor, including defensive ends Stephen Weatherly and Tashawn Bower, were part of the reason he was expendable to the Vikings.

"We felt like those two young guys had a chance to be good players," Zimmer said. "Obviously, it was tough about Brian. Since I've been here, he's been a great mentor, a good player, worked hard every day. So, unfortunate it's part of the NFL."

Weatherly expanded on Robison's mentorship, which happened on and off the field.

"Most times, when a guy mentors a guy, it's just football," Weatherly said. "Maybe he doesn't have that attitude to address him as a man. Like, 'Hey, how are you doing? How are things back home? Where's your head space at right now?' I was able to have that with B-Rob."

His 'natural position'

Second-year guard Danny Isidora might not be called a guard anymore. After he started at center in the preseason finale in Tennessee, the Vikings liked his play and are keeping him there during practices this week, according to Zimmer. With starter Pat Elflein not ready for Sunday's opener, quarterback Kirk Cousins will take snaps this week from a center he hasn't yet played with in a game.

"I think that might be a natural position for him," Zimmer said. "He's never done it before, and for him to do it in basically a week I thought it's been impressive. It's been good this week, as well."

Zimmer added guard/center Brett Jones, acquired from the Giants last week, was also "impressive" as he played at both left guard and center against the Titans.

Mack to Chicago

The Vikings weren't exactly elated that premiere edge defender Khalil Mack was traded from the Raiders to the Bears over the weekend. Mack has 40½ sacks in four NFL seasons.

"Probably wish he wouldn't have went to Chicago," Zimmer said. "Obviously the division is really good, but he adds another dimension to their defense that was already pretty good."

Practice squad full

Tight end Cole Hikutini was signed to the Vikings practice squad on Monday, completing the 10-man group entering the regular season. Hikutini, 24, spent last season with the 49ers — the Vikings' opponent on Sunday — after going undrafted out of Louisville.

Number changes

For those keeping track, four Vikings changed numbers entering the regular season. Receiver Chad Beebe will now don No. 12 on the practice squad. Safety George Iloka has changed to No. 23. Cornerback Holton Hill will wear No. 24 and defensive tackle David Parry will wear No. 95.