Draft an inexact science? Not for these five teams

In many ways, rating the draft evaluators heading into the 2008 scouting combine is no different from identifying the teams with the best chance to win. Teams are built through the draft, so those with the best core players acquired through the draft are the teams usually at the top of the standings.

The key is continuity. In a league that averages seven head-coaching changes a year, the top franchises keep their head coaches and aren't going through the annual mess of changing coordinators and philosophies. By maintaining continuity, draft evaluators know the type of athletes that fit their team's systems, which is a big advantage.

This league isn't that complicated. You need a great quarterback and enough talent on defense to give that quarterback a fighting chance on a weekly basis.

Here are the top five draft evaluators heading into the combine.

1. New England Patriots -- Of the top five, the Patriots have the fewest of their own draft choices on the roster (27), but that's only because their roster doesn't provide many openings. Coach Bill Belichick and general manager Scott Pioli know exactly what they want every year. Despite an abundance of draft choices in 2007, both knew first-round safety Brandon Meriweather was the only rookie with a chance to stick. Belichick needs smart, versatile players who fit his offensive or defensive system.

As evaluators, they are patient and smart. The offensive line was built through the draft. Now, New England has three Pro Bowl offensive linemen. The defensive line has three former first-rounders. Belichick finds role players for his secondary who give him a chance to adjust game plans and personnel for each game. No coach in football does a better job of knowing the strengths and limitations of the players on his roster. In the draft, Belichick and Pioli might not go for the big names, but they find the smart player who can learn and fit within the team concept. It's one of the big reasons the Patriots have a 91-37 regular-season record since 2000, best in football.

2. Indianapolis Colts -- Bill Polian has a different challenge than that of just about any other general manager in football. Thanks to Peyton Manning, the Colts have a big portion of the salary cap invested in offense. Polian drafted Manning in 1998 and built the franchise around him. To keep the offense at the top of the league, he shifted the economics of the team to make sure Manning had the right pass-blockers and pass-catchers. The strategy has worked for eight playoff seasons in 10 years, but it also has its drawbacks.

Top young defenders usually have to leave once their rookie contracts expire. Through the years, Indianapolis has lost top linebackers such as David Thornton, Mike Peterson and Marcus Washington. Starting cornerbacks Jason David and Nick Harper were lost from the 2006 Super Bowl team.

Despite that, Polian keeps finding players. He rarely misses on a first-round choice, and his defense is loaded with good, young athletes acquired from the draft.

3. San Diego Chargers -- General manager A.J. Smith has built a powerhouse that should contend for championships for the next several years. Rarely does he use free agency to fill needs. In fact, he understands the dynamics of the draft and places a high premium on compensatory draft choices. Cornerback Drayton Florence and running back Michael Turner are examples of successful draft choices who will leave as free agents this winter and add compensatory picks in 2009.

Smith is always looking to the draft to make the team better. He used the Eli Manning trade to net three Pro Bowlers through the draft: quarterback Philip Rivers, linebacker Shawne Merriman and kicker Nate Kaeding. The Chargers are loaded, but Smith will find more athletes in the 2008 draft who will make them better.

4. Pittsburgh Steelers -- Stability has been the strength of the Steelers. Under former coach Bill Cowher, Pittsburgh kept stockpiling linebackers and letting them sit a year or two to learn the 3-4 scheme. Before long, those linebackers became stars. Top personnel man Kevin Colbert is one of the best in the business at filling needs though the draft. The Steelers' offense line has been built mostly on draft choices. The secondary is primarily a byproduct of the draft. The team might sign a veteran free agent, if needed, but the mission is to build the team through the draft and identify the best young players for contract extensions.

The system won't change under current coach Mike Tomlin. Pittsburgh has 31 draft choices on its roster, including 23 from the top four rounds. Because the Steelers are usually thinking ahead, they don't get caught in situations in which they need more than four new starters in any given offseason. The Steelers know how to stockpile talent through the draft and, with Ben Roethlisberger at quarterback, Pittsburgh will be an annual Super Bowl contender.

5. Baltimore Ravens -- This fifth position is up for grabs. The Packers, under GM Ted Thompson, are knocking on the door of the top five thanks to his recent drafts. Despite the Jaguars' failures to find impact skilled players on offense in the first round, they're also knocking on the door, thanks to their ability to draft quality players. Jacksonville had 36 drafted players on its roster at the end of the 2007 season.

But it's hard to knock Ravens GM Ozzie Newsome out of the top five. He has a league-high 10 first-round draft choices on Baltimore's roster. He built one of the era's best defenses through the draft, grabbing Pro Bowl player after Pro Bowl player in the first round. The only problem the Ravens have is at quarterback. Kyle Boller, a former first-rounder, hasn't lived up to his potential, so the team had to trade for Steve McNair to produce a 13-win season in 2006. If Baltimore can strike gold at quarterback through the draft, the drafted talent base is good enough for 10 or more wins each season.

John Clayton, a member of the Pro Football Hall of Fame writers' wing, is a senior writer for ESPN.com.