What does a team do after it gives up a third-round draft choice for a once-productive goofball that the smartest man in the NFL has decided is no longer worth the trouble? In this case, it uses a fourth-round draft choice to take a player who reportedly tested positive for marijuana two months earlier at the league's mass audition for prospects.

The Vikings erred grievously by allowing New England's Bill Belichick to convince them to give up the third-rounder for the burnt-out Randy Moss last October. And they still were attempting to make up for the blunder when the NFL entered the third day of its draft marathon Saturday.

The bounty after three rounds was quarterback Christian Ponder and tight end Kyle Rudolph, and that had increased the talent gap the Vikings faced in the NFC Central vs. Green Bay, Chicago and even Detroit at the end of last season.

The Vikings went for the talent in the fourth round as well as another Christian -- this one Ballard, a defensive lineman from Iowa. The early projections had him as a second-rounder, but that was before Ballard apparently told teams at the NFL combine that he expected to test positive for marijuana.

Ballard also had expected his Hawkeyes to beat the Gophers at the end of last season, but this time he was right ... about the positive drug test.

On Saturday, Ballard was on a conference call and question No. 5 from the media was: "There were reports that you failed a drug test at the combine. Do you think that caused you to slide in the draft?"

Ballard: "I'm not really sure what caused that. I've made mistakes in the past, but I'm going to look to the future. I'm a Viking now. Whatever happened in the past is behind me."

Reporter: "Were those reports accurate?"

Ballard: "That's confidential. I'm just not willing to speak about that now."

There's something about the Vikings, defensive linemen and the fourth round. A year ago, they went for Southern Cal's Everson Griffen, a defensive end with off-field "concerns."

Griffen had two run-ins with the law in Los Angeles within a 48-hour period three months ago. The good news is that he had to be Tasered twice to be subdued, so it would seem Evie's staying in shape.

As for Ballard, there are two ways to look at it: A) How smart is a guy who can't stay off the weed before the combine? And B) Have you ever heard of a dumb cellist?

"My great uncle [was] Hank Ballard, a musician," Ballard said. "He wrote 'The Twist.' Hank Ballard & the Midnighters. ... That's something our family takes pride in.

"I play the cello and the bass. I do a little bit of the music and the arts ... My mother actually put me on the cello, and I was kind of a natural at it."

Ballard was part of an all-senior defensive line that was supposed to lead the Hawkeyes to a grand fall. End Adrian Clayborn was the star, with Ballard, Karl Klug and Broderick Binns as his running mates.

Clayborn was taken 20th overall by Tampa Bay on Thursday. Klug, from Caledonia, Minn., was drafted in the fifth round by Tennessee on Saturday. Binns, from Cretin-Derham Hall, was replaced as an Iowa starter by junior Mike Daniels.

The ESPN and Big Ten Network analysts would gush incessantly about Iowa's front, and then viewers would watch opponents put together late and long drives to steal away victories.

The Hawkeyes lost five games in the fourth quarter -- including the loss of Floyd of Rosedale in the season finale at TCF Bank Stadium.

In 2009, the same front line led an Iowa defense to 31 sacks and 74 tackles for loss. In 2010, the numbers were 21 and 57. Ballard went from 5 1/2 sacks and nine TOLs in 2009 to three and five last season.

Watching Northwestern put together late drives and basically ruin the Hawkeyes' season gave a suspicion that Iowa's defensive front was highly overrated. Watching the Gophers do the same a couple of weeks later turned it into more than a suspicion.

The Vikings are pleased to have Christian Ballard, and you certainly would prefer to have used the 106th overall selection on one of those underachieving Hawkeyes rather than the 20th, as did Tampa Bay with Clayborn.

Patrick Reusse can be heard noon-4 weekdays on 1500ESPN. • preusse@startribune.com