Teams picking at the end of the first round are lucky to find someone capable of becoming a starter, much less an All-Star. Most of the guys available are replacement-level players: capable of defending their position and not killing you on the offensive end, but unable to consistently create their own shot or play elite defense at multiple positions.

So if there isn’t a large gap in talent between two players, late first-round teams are almost always better off selecting the bigger one. There aren’t many men in the world with the height needed to play in the NBA; there are even fewer that also have the necessary athleticism, skill-set and desire. Only 5% of American males are taller than 6’3, while the CDC’s statistics on height suggest there are only 70 native-born seven-footers between the ages of 20 and 40 in the entire US.

You can find a replacement-level point guard in the D-League; there aren’t enough replacement-level big men to fill 30 NBA rosters.

The Portland Trail Blazers faced this situation with the 21st pick in this year’s draft. While much of the pre-draft speculation had them linked to Morehead State’s Kenneth Faried, an elite 6’8 225 rebounder, they surprised many by taking Duke’s Nolan Smith, a 6’3 200 combo guard, instead.

Neither Faried nor Smith projects to be a front-line starter. Faried has almost no perimeter game to speak of whatsoever, and at only 6’8, isn’t tall enough to play exclusively at center. Smith isn’t a true point guard, and at only 6’3, isn’t tall enough to play exclusively at shooting guard.

Both are college seniors who should be able to contribute right away off the bench. But a third big man is far more valuable than a third guard, which is why Portland should have taken Faried.

With Greg Oden’s health still very much in question, the Trail Blazers don’t have a single big man they can count on behind Marcus Camby and LaMarcus Aldridge. They’re not the only playoff-caliber team in that boat either: the first big man off San Antonio’s bench is Matt Bonner, the first one off of New Orleans’ last year was Jason Smith.

Having a quality reserve post player isn’t cheap: the Mavericks gave Brendan Haywood a $55 million contract last summer; the Heat gave Udonis Haslem more than $20 million. In contrast, in Game 6 of the NBA Finals, both teams started guards earning less than $2 million a season. One was a second rounder (Mario Chalmers) and the other wasn’t even drafted (JJ Barea).

Now Portland has to enter the shallow pool of free-agent big men whenever the CBA is resolved, possibly without any kind of salary-cap exceptions. The sure things (Tyson Chandler, Nene, Marc Gasol) will want contracts upwards of $10 million a year, and with playoff teams like Atlanta and New York desperate for size, even guys like Sam Dalembert and Kris Humphries will be looking for at least $5 million.

Contrast that with Denver (Faried) and Boston (JaJuan Johnson), who took athletic young big men that Portland passed on, and now have them locked in on rookie-deals for the next four years. If some form of a hard cap is instituted in a new CBA, a 6’8+ player who can soak up interior minutes on a team-controlled contract will be one of the most valuable assets in the league.

By the second round, teams were reaching on big men with serious defensive questions (Jon Leuer, Justin Harper) and conditioning issues (Jordan Williams, Trey Thompkins). Meanwhile, the pool of guards was still strong: at least three combo guards taken in the second round -- Butler’s Shelvin Mack, UCLA’s Malcolm Lee and Hofstra’s Charles Jenkins -- were roughly the same level as Smith as prospects. Illinois’ Demetri McCamey, a 6’3 point guard with a better assist/turnover ratio than Smith, and Ohio State’s David Lighty, a much more athletic 6’5 guard who will be just as effective off-the-ball as Smith, weren’t even drafted.

And while Faried would have walked right into a significant role in Portland’s rotation, Smith will have to beat out last year’s first rounder (Elliott Williams) as well as two second-rounders (Armon Johnson and Patty Mills) who have shown something at the NBA level.

Which isn’t to say that Smith is a particularly bad pick, if you can get an NBA-level contributor at No. 21 you’ve done something right. But there are a lot of places you can find an NBA-level combo guard: the Spurs picked up Gary Neal as an European free agent, while perimeter players constitute the vast majority of NBDL call-ups who’ve stuck in the league.

There’s no guarantee Portland will be able to take a big man of Faried or JaJuan Johnson’s caliber in next year’s draft, but it’s almost a certainty they’ll be able to take a guard of Nolan Smith’s.