The entire football world was stunned the night before the 2006 NFL draft, when the Houston Texans announced they would pass on USC running back Reggie Bush to use the first overall pick on defensive end Mario Williams. Instantly, one of the biggest debates of the off-season became, “How much will Houston regret its decision?”

Even those who expected Williams to become the more valuable player down the road admitted that Bush would have the better rookie season — after all, running backs generally have the easiest transition to the pro game from the college game. Each time Bush made a spectacular highlight-reel play, went the popular theory, Texans fans would light up the phone lines of Houston talk radio with complaints.

But it hasn’t worked out that way. Not only is Williams clearly outplaying Bush, but both are being overshadowed by a number of excellent rookies chosen much later. The greatest impact of all has come from Bush’s teammate, the player chosen 252nd in the draft, Hofstra’s Marques Colston.

Before the draft, Colston was considered too slow to play wide receiver in the pros. Draft analysts acknowledged that Colston ran good routes and had good hands, so most people expected him to convert to tight end. His size would allow for it if he could put on more muscle, and it would be easier to get open against linebackers rather than cornerbacks.

But the Saints took one look at Colston in training camp and realized smart route-running will get a receiver open far more often than raw speed. They stuck him back at his natural position and may end up with one of the greatest draft steals of all time.

With 869 yards and seven touchdowns, Colston is actually on pace to break the 46-year-old NFL record for receiving yards by a rookie (which isn’t even an NFL record, really). Bill Groman set the record with 1,473 yards for the Houston Oilers of the AFL in 1960, but the AFL-NFL merger also merged the record books of the two leagues.

Colston’s success has allowed Saints fans to overlook Bush’s problems. Some analysts argued before the draft that Bush could never succeed as an everydown back in the NFL, but even the biggest Bush detractors could never have imagined just how much he would struggle in his first season.

Bush is averaging just 2.8 yards a carry, the lowest figure of any running backs with at least 40 carries this season. On first downs, he’s even worse, just 2.3 yards a carry. Bush is doing better as a receiver, but even there he’s below average. Bush is averaging 6.6 yards a reception, lower than the league average for running backs, which is 7.5 yards.

Bush’s numbers are even more stunning because his backfield partner, Deuce McAllister, is having a reasonably good season behind the same offensive line and averages 4.3 yards a carry. New Orleans’ offensive line seems better suited to a more straight-ahead running style, which McAllister is exhibiting this season after his ACL injury last year took away some of his lateral movement. Nonetheless, Bush is struggling in large part because in the NFL, the blockers can’t open up holes as wide as is done in college, and the holes are often closed by the time Bush has run up to the line.

Williams is doing better, but he’s not blowing the league away either. He does lead the Texans with 4.5 sacks, and he has played very well against the run. But the Texans are still one of the weakest pass defenses in the NFL.

Williams and Bush are not alone. The other top picks in the draft are also clearly players in development, rather than players who were ready to burst onto the scene as rookies. Vince Young may be the farthest along, but he’s completing fewer than half his passes in Tennessee. D’Brickashaw Ferguson is coming along at left tackle for the Jets, but he certainly hasn’t had the impact of the past rookies he was compared to before the draft, like Orlando Pace and Jon Ogden. Tight end Vernon Davis, the sixth pick, has missed almost the entire season due to injury.

That’s not to say that no first-round picks are playing well this year. Kamerion Wimbley, for example, has been excellent in Cleveland. San Diego cornerback Antonio Cromartie is much less of a project than analysts expected. Running backs Laurence Maroney and Joseph Addai are both important players for playoff-bound teams.

Nonetheless, the top candidates for Rookie of the Year are almost all players taken in the later rounds of the draft. None has surprised more than Colston, but he wasn’t the only rookie to get a starting job right out of the gate. Greg Jennings, chosen by Green Bay in the second round, beat out a host of veterans to start opposite Donald Driver, and he has 485 yards so far despite missing one game due to injury.

On the offensive line, the best rookie is not Ferguson but San Diego’s secondround pick Marcus McNeill, who has started every game at left tackle. Meanwhile in Green Bay, the Packers have seen dramatic improvement on the offensive line, in large part due to two rookie guards who have started all year: third-round pick Jason Spitz and secondround pick Daryn Colledge. And New England’s Ryan O’Callaghan, a fifthround pick, has been starting at right tackle since the first week of the season.

The top rookies on defense are also lower-round picks. Barry Cofield, chosen in the fourth round by the Giants, has started every game at defensive tackle and seamlessly replaced departed free agent Kedrick Clancy. Second-round linebacker Thomas Howard is a big part of the improving Oakland defense (which nobody is noticing because the Oakland offense is so horrible).

No position has seen as many solid rookies as safety. Strong safety was a gaping hole in the otherwise talented Baltimore secondary, but that hole has been filled by fifth-round pick Dewan Landry. Buffalo fourth-rounder Ko Simpson and Indianapolis sixth-rounder Antoine Bethea have also been starters for most of the season.

If every team could spot these lateround gems with more accuracy, of course, they wouldn’t be taking them in later rounds. But the success of these lower-round picks is an argument for spending more money on scouting. It’s much cheaper than handing out big free agent signing bonuses, and no player brings more value per dollar spent than a low-round draft pick who becomes a starter.

Mr. Schatz is the editor in chief of FootballOutsiders.com.