Shortly after Case Keenum stepped into the Vikings first-team huddle in September, he let the team’s wide receivers know things were going to work a little differently.

“That was something he kind of emphasized in practice: ‘Hey guys — make sure you’re staying alive, because I like to get out of the pocket,’ ” wide receiver Adam Thielen said. “[It’s] making sure that [he’s] extending plays and making sure that us as receivers are getting open when he does.”

Keenum’s mobility, used to stress defensive coverages and create big plays downfield, has become a major part of the Vikings offense as the quarterback has put his stamp on the team during the first half of the 2017 season. According to Pro Football Focus, he is third in the league on throws outside the pocket, with a passer rating of 114.1.

Four of his seven touchdown passes have come on throws outside the pocket; on Sunday, as the quarterback rolled to his right, Thielen slipped into a hole in the Cleveland Browns’ Cover 2 scheme, standing alone in the corner of the end zone as cornerback Jamar Taylor passed the receiver off in coverage and safety Ibraheim Campbell came too late to cover Thielen.

It was an easy score on a pass that might not have gotten to Thielen had Keenum not broken the pocket for some extra time.

“My read was on the other side, and I just wound up coming back to him on the little scramble drill,” Keenum said Sunday. “It’s good because he probably would have let me have it if I hadn’t seen him and thrown him the ball. I did a good job of finding him in open space and being in the right position.”

In Keenum’s first game as a starter, his mobility might have worked to his detriment, as he often dropped too deep in the pocket against the Steelers and was quick to bail outside of it on several occasions. Now that he’s in better sync with the Vikings’ protection schemes, he’s been able to use his mobility to great effect this season, whether it’s on a designed rollout or a play where he’s looking to improvise.

“It’s kind of always been a part of my game, the scramble drill,” Keenum said. “Sometimes those are planned, getting out of the pocket. But I think any time those guys have to guard our guys for longer than the two or three seconds that a normal pocket is healthy, once you get out of the pocket, it’s really tough, as you guys saw on Sunday.”

It resembles backyard football at times, but few things in the NFL are ever that improvised. For Vikings receivers, even as they’re trying to get open when Keenum breaks the pocket, there are rules to where they’re going.

“You’re trying to roll [to his side], because he’s not going to throw the ball all the way across the field, especially to a receiver — maybe to a back that’s just leaking out of the backfield or something like that,” Thielen said. “You’ve got to roll toward him, and then you kind of have to keep even spacing between you as a receiver, because there’s going to be a lot of receivers on that side of the field. You need a guy that goes deep, a guy that goes short and a guy in the middle.

“Sometimes it’s just kind of looking out in front of you, seeing where other guys are and adjusting off of that.”

Thielen on Keenum The wide receiver lauds the quarterback's preparation. VideoVideo 03:43

The Vikings had implemented more rollouts for Sam Bradford during training camp, and it seemed like they might try to get him outside the pocket in the regular season. They’re used to that being part of Teddy Bridgewater’s game, too, though Bridgewater would have to re-establish timing and trust with receivers should he wind up as the Vikings quarterback later this season.

While Keenum is running the offense, though, he’s making his mobility a staple of his game. And as Vikings receivers learn to expect it, they’re making it a central plank of their offense.

“Case can make things happen with his feet, and it’s something that we’re getting more used to, something that we’re actually practicing during the week,” tight end Kyle Rudolph said Sunday. “And it’s huge for us as an offense if he can extend those plays. We can create those opportunities that add one more thing we can do to defenses in the red zone and make it tough for the defense.”