Kirk Cousins is looking sharp in spring practices, but he's learning precisely what "open" means in his new offense.

Cousins passed up Vikings tight end Kyle Rudolph during a red-zone drill in Wednesday's organized team activity practice. Rudolph wouldn't have been the first receiver to say he was left open. But quarterbacks coach Kevin Stefanski thought Cousins missed the window for a big play and let him know afterward.

"Hey, in that situation, you might want to give Kyle a chance," Cousins recalled hearing from Stefanski, "even though he looks covered. You have to throw him the ball. He's open."

The Vikings' passing game remains an obvious work in progress after just five 11-on-11 practices into Cousins' tenure. While the veteran quarterback found receivers Adam Thielen and Laquon Treadwell for impressive strikes, he's still adapting to nuances of each target. They range from an effective close-quarters tight end such as Rudolph to some shifty receivers.

Jump-starting that chemistry is a continued emphasis in the red zone, where the Vikings will rely on a new quarterback and new coordinator to maintain their 2017 success.

Zimmer first made those game situations a big part of practices last offseason after three years of poor play by the Vikings offense. During Wednesday's practice, the Vikings devoted many full-team snaps to practicing red-zone third downs.

Without shoulder pads or full contact in this portion of the offseason, it's essentially a passing camp for Cousins & Co.

"We've spent an awful lot of time, I think this is our fourth day in the red zone," Zimmer said. "I think it's just important we get a lot of work in there. We put a big emphasis on it last year. We're going to continue to do so."

The red zone is where the 2017 Vikings thrived with Case Keenum and Pat Shurmur. Only four offenses scored more than the Vikings' 5.11 points per red-zone trip last year, according to Football Outsiders.

That included five touchdowns from inside the 10-yard line against Cousins' Redskins in a 38-30 victory in Washington.

Shari L. Gross
Video (01:35) The Vikings continue to get used to new play strategies and each other during OTAs.

Red-zone success wasn't as automatic for Cousins and Redskins coach Jay Gruden. Washington ranked ninth, 28th and 14th in points per trip during the quarterback's three seasons.

Cousins didn't get much help from his run game in Washington. He actually led the Redskins in rushing touchdowns (14) from 2015 to '17, including seven scores at the goal line.

The Vikings had 10 rushing touchdowns at the goal line last season.

"That's why we're doing it. It's not easy," Cousins said. "It is condensed. You have to be on the screws. Your throws have to be that much more accurate.

''The routes have to be that much more perfect in terms of the depth, the cut and the timing. That's why we're practicing it right now."

The burden falls primarily on the shoulders of Cousins and first-year coordinator John DeFilippo, the former Eagles quarterbacks coach. The Vikings were swayed to hire DeFilippo, in part, because of his weekly role planning Philadelphia's red-zone attack that ultimately won the Super Bowl.

Coaches have spent the past seven weeks installing DeFilippo's offense. It's an amalgamation of DeFilippo's influences and elements of what worked under Shurmur.

But "everything is new" to Cousins, as Zimmer said, which adds additional layers to his acclimation. He had to learn new snap counts and play calls before even trying to establish a rapport with his receivers.

Cousins has now begun his work in earnest with NFL rules allowing the Vikings to practice full team drills. Perhaps there's no better measuring stick for his progress than in the red zone, where the slightest hesitation can throw off chemistry and an offense's chances.

"Each play helps build a confidence," Cousins said. "Helps build a rapport with the receivers, with the tight ends. Try to get on the same page with the centers, protection calls. It is a lot of new, a lot of chemistry that still has to be built."