Branch, Okoye worth the risk?

During his long and distinguished tenure as New York Giants general manager, George Young, as deft with a quip as he was at identifying player prospects, often operated in the draft on what he termed the Planet Theory.

The premise was a simple one: There is a finite number of athletic, 300-pound people, Young posited, walking around on planet Earth. And if you have a chance to grab one of those rare human beings in the draft, you'd better take advantage of the opportunity.

On paper, the Planet Theory makes sense, it seems. On the field, it was certainly successful for Young, whose many strengths included finding solid offense and defensive linemen, and whose acumen helped deliver a pair of Super Bowl championships to a storied franchise.

But the Planet Theory hasn't worked as well in application for other teams in the draft, and at no position is that manifested more than at the defensive tackle spot.

Even with the recent infusion into the league of standout young defensive tackles such as John Henderson and Marcus Stroud of Jacksonville; Chicago's Tommie Harris; and Richard Seymour and Vince Wilfork of New England, the position remains among the hardest to fill. And for scouts, as recent history indicates, certainly among the most difficult to handicap.

"It's probably the position where teams make the most mistakes," Kansas City coach Herm Edwards acknowledged at the annual owners meetings last month. "A tackle can be the most dominating player on the field and, because there are usually so few of them, people will go out and 'reach' to try to get one. You always seem to be projecting with tackles, you know, maybe more than any position. It's like, 'OK, I know he can't do this, this or this, but he has some upside and he'll grow into the position.' But there are sure a lot of misses at the position, especially in the first round."

Indeed, investing a high-round draft choice on a defensive tackle can bring the promise of great reward -- and, unfortunately, of immense risk as well.

"It can definitely be a 'boom or bust' position," said Detroit coach Rod Marinelli, who earned his stripes as one of the league's best and most innovative defensive line coaches during his time as an assistant at Tampa Bay. "[It's] really hit-and-miss, you know?"

This year's draft doesn't figure to be much different.

Consider the player who for most of the 2006 college season was regarded by scouts as the top defensive tackle prospect in the draft, Alan Branch of Michigan, but whose stock seems to be devalued almost daily as the lottery draws closer. Like a lot of players at a position that annually produces far more than its share of underachievers, Branch is a prospect who appears to be too unmotivated at times and whose competitive motor doesn't consistently rev at a high level.

Noted St. Louis coach Scott Linehan, rather candidly, of Branch: "He's the best [prospect at tackle], but he doesn't always play like the best."

Add to Branch's maddening deviation of effort the fact there are now health questions -- some teams feel the former Wolverines star has stress fractures in both legs, and other clubs have diagnosed the problem as shin splints -- and the risk factor is magnified exponentially. Branch will still be a first-round selection, but the consensus now is that he could easily slip out of the top 10.

The other highly regarded tackle prospect, Louisville's Amobi Okoye, is only 19 years old. He is also one of the three players alleged to have acknowledged past marijuana use during the combine interviews. That alleged indiscretion might not be as significant a factor for scouts as Okoye's age. He will be the youngest player ever selected in the modern era draft, and though his maturity is estimable, the fact is he's barely old enough to vote, let alone decide which gap to slant into on the pass rush.

Which is why some tackles with solid second- or third-round grades -- Justin Harrell and Turk McBride (both of Tennessee), Tank Tyler (North Carolina State), Paul Soliai (Utah), Ray McDonald (Florida) and Ryan McBean (Oklahoma State) -- could be relative bargains in next weekend's draft.

Lately, the second round has produced standout tackles such as Kris Jenkins of Carolina and Detroit's Shaun Rogers and, although both those Pro Bowl performers broke the bank with their second NFL contracts, the original financial exposure for their teams wasn't great. Part of the trade-off in choosing a tackle in the first round is that any franchise is going to pay a premium for selecting a player so high and that the team is out a lot of money if the prospect turns out to be a bust.

In 2006, the Philadelphia Eagles paid nearly $8 million in various bonuses and base salary to defensive tackle Brodrick Bunkley, the 14th player chosen overall, as part of his rookie contract. Bunkley didn't start a single game, registering a measly nine tackles and no sacks. The Eagles got nearly as much production from LaJuan Ramsey, a tackle chosen in the sixth round who earned just $348,000 as a rookie.

The Giants unearthed tackle Barry Cofield in the fourth round. He started in all 16 games and notched 44 tackles while earning only $679,625 in signing bonus and base salary money. Washington chose Kedric Golston in the sixth round, paid him only $340,575 as part of his rookie contract, and he started 12 games and had 42 tackles. In fact, of the five tackles chosen in the first three rounds of the 2006 draft, the only one to have anything resembling an impact was Haloti Ngata, and the Baltimore first-rounder wasn't nearly as dominating a defender as scouts felt he would be.

"You just don't get many guys at the position who walk right onto the field at our level and make a huge difference," said Ravens GM Ozzie Newsome. "It's a really hard position to play. And it's a really hard position to scout. It's just the nature of the beast that teams seem to make a lot of mistakes on defensive tackles."

The numbers bear that out.

Since 2000, there have been 26 defensive tackles selected in the first round and 59 chosen as first-day picks. Only six have played in even one Pro Bowl game, and 15 are out of the NFL entirely right now. The 2001 draft produced five of the six Pro Bowl tackles chosen since 2000 -- Seymour, Stroud, Casey Hampton, Jenkins and Rogers -- and the league might never see such a bounty at the position again.

Len Pasquarelli is a senior writer for ESPN.com.