Donovan McNabb’s longest pass completion with the Vikings was a screen to running back Toby Gerhart, who rumbled 42 yards last week against Tampa Bay.

Hardly a novel play call and yet another reminder that the vertical passing game Brett Favre used to terrorize opponents in 2009 is a distant memory.

To be sure, the Vikings are built offensively to run on the legs of Adrian Peterson, who gashed the Buccaneers for two touchdowns and 120 yards in Minnesota’s 24-20 loss.

But evidence is mounting that the Vikings (0-2) either do not have the playmakers to threaten defenses downfield or their playmakers simply are not up to the task.

Entering Week 3 against undefeated Detroit, only the Kansas City Chiefs are averaging fewer yards passing than Minnesota’s 120. Questions are being raised about McNabb’s accuracy; the lack of involvement of the Vikings’ most talented receiver, Percy Harvin; and the jelling of the offense under new coordinator Bill Musgrave.

“We are still learning one another and learning a lot about our players and particularly the new coaches,” coach Leslie Frazier said Wednesday. “We need to get it to the point where we’re where we want to be. We’re not quite there yet, but we’re getting closer.”

Harvin leads the receiving corps with nine catches for 83 yards, including a 19-yard reception against the Bucs. Newcomer Michael Jenkins has six catches for 55 yards, including a touchdown in the Week 1 loss at San Diego.

But Bernard Berrian, expected to rebound from an unproductive and injury-plagued 2010 season, has only one catch for 17 yards. Tight end Visanthe Shiancoe has been limited to three receptions and 28 yards.

McNabb, who rebounded from a career-low 39-yard passing game against the Chargers to throw for 228 against Tampa, has been unable to connect with his receivers on several patterns of 10 or more yards.

Against the Bucs, he threw behind Berrian and overthrew Shiancoe in the first quarter, misfired later on two attempts to Devin Aromashodu, and threw incomplete to Harvin on the Vikings’ last possession in the final 30 seconds.

Frazier was asked if McNabb had progressed to where he thought the quarterback would be after two weeks.

“He’s probably just about where I expected him to be. To see him come back after a tough one that first ballgame, to bounce back the way he did and lead us in the way he did, was really encouraging and kind of what I expected,” Frazier said.

“And I expect him to just get better and better as the year goes on. I expect him to have a good game on Sunday, as well.”

NFL quarterbacks are racking up huge passing numbers this season while the Vikings have stalled badly on offense in the second half of each loss.

McNabb insisted there were enough big plays made in the passing game against Tampa, at least in the first 30 minutes, and that there will be opportunities to strike downfield.

“I think people are seeing teams throwing deep balls for 60-, 70-yard touchdowns, and that’s going to come,” he said, “but you have to methodically move the ball downfield and move the chains, and we were able to do that.

“I don’t believe in throwing the ball just to throw it, throwing it up for grabs. If it’s there, you take advantage. If you have the right play call at that particular time and it’s there, you take advantage. It could work out for you, it may not. But they will know that you’re going to be able to establish downfield, and from then on you set up some intermediate passing gains, you run some screens, you get your tight ends involved vs. linebackers and safeties.”

Frazier pushed back against criticism that the Vikings are not deploying Harvin enough in the passing attack because they are trying to get others the ball.

“There’s nothing he has to prove. We know what Percy is capable of doing,” Frazier said. “I think we’ve taken the right approach with Percy with his reps and the packages that we use him in. It’s the right approach.”

Said Harvin: “There are plays left out there and plays made. No team’s going to make every single play. There’s definitely some things we’ve got to correct as a team. We’re working hard to get it done. It’s not a lack of effort.”

Follow Brian Murphy at twitter.com/murph1171