The 2012 NFL Draft starts Thursday with NFL teams taking the opportunity to draft the best talent from the college ranks into the pros. While many teams build Super Bowl champions by drafting blue chip prospects, many other great players are left undrafted. Here are 15 of the best undrafted players in the NFL today:

Arian Foster, Houston Texans

Arian Foster

After having a sub-par senior year at Tennessee, running back Arian Foster went undrafted in 2009. The Houston Texans signed Foster to a free agent contract and gave him a chance to start in 2010. All Foster did was become the NFL rushing champion and Pro Bowl running back with 1,616 yards. He added another Pro Bowl nomination and 1,224 yards in just 13 games in 2011. The Texans rewarded Foster’s efforts with a new five-year contact in March.

Wes Welker, New England Patriots

Wes Welker

A 2004 Texas Tech product, wide receiver Wes Welker has become one of the most prolific pass catchers in the NFL. While Welker does benefit from playing in the pass-happy New England offense, it’s hard to deny the ability of a guy who has led the NFL in receptions three times. Bitter Patriots fans, though, will remember the catch Welker didn’t make against the Giants in February’s Super Bowl, but receivers don’t come much better than him.

Tony Romo, Dallas Cowboys

Tony Romo

Not all quarterbacks are first-round draft picks, but Dallas Cowboys’ starting quarterback Tony Romo wasn’t drafted at all when he came out of Eastern Illinois in 2003. While Romo has yet to have true playoff success for Dallas, he has evolved into a 4,000-plus yards-per-season passer with a career QB rating of 96.9. If Romo can ever add a Super Bowl ring to his three Pro Bowl appearances, he could be remembered as an all-time Cowboys great.

Victor Cruz, New York Giants

Victor Cruz

With a tremendous 2011 season, New York wide receiver Victor Cruz went from the practice squad to the Super Bowl. After going undrafted out of the University of Massachusetts in 2010, Cruz was able to stick around the Giants organization long enough to step into an opportunity to shine this season. His 1,536 yards and nine scores were a key part of New York’s championship season.

James Harrison, Pittsburgh Steelers

James Harrison

Known for his ferocious hits and intimidating presence, linebacker James Harrison was not drafted after he left Kent State in 2002. A decade later, Harrison is a key part of Pittsburgh’s elite defense and an outspoken leader of the team. During his career, Harrison has been to the Pro Bowl five times and won two Super Bowl rings with the Steelers.

Antonio Gates, San Diego Chargers

Antonio Gates

A physical marvel who didn’t merit a draft selection in 2003 after playing basketball at Kent State, Antonio Gates has all but revolutionized the tight end position since entering the NFL. He has been to the Pro Bowl eight times and is still a matchup nightmare for opposing teams who can’t find anyone fast, strong or tall enough to cover him in the red zone. Gates has a legitimate shot at the Hall of Fame after he retires.

Fred Jackson, Buffalo Bills

Fred Jackson

Undrafted in 2002 while coming out of tiny Coe College in Iowa (and the World Football League), running back Fred Jackson was a force for the Buffalo Bills in 2011 prior to being injured. Despite playing in just 10 games last season, Jackson rushed for 934 yards and six touchdowns. He has averaged 974 yards per season over the past three years.

Ryan Clark, Pittsburgh Steelers

Ryan Clark

Despite a solid college career at LSU, safety Ryan Clark was not selected during the 2002 NFL Draft. While most of the NFL teams could use his big hitting presence in the secondary, Clark now plays for the Steelers after earlier stops with the Giants and Redskins. His 100 tackles helped give Pittsburgh one of the league’s best defenses in 2011.

Jason Peters, Philadelphia Eagles

Jason Peters

Though he will miss the 2012 NFL season due to a ruptured Achilles tendon, tackle Jason Peters of the Philadelphia Eagles is one of the best offensive linemen in the game. With his incredible skill set, it’s a wonder how the five-time Pro-Bowler wasn’t picked by any team after he left Arkansas in 2004. The Eagles will miss Peters and hope that he comes back stronger in 2013.

Jeff Saturday, Green Bay Packers

Jeff Saturday

After a 13-year career in Indianapolis that included five trips to the Pro Bowl, center Jeff Saturday is no longer a member of the Colts. Saturday will give depth to the Green Bay Packers’ offensive line in 2012, but Colts fans will always consider this 1998 North Carolina product one of their all-time greats.

Josh Cribbs, Cleveland Browns

Josh Cribbs

While many teams noticed Josh Cribbs at Kent State, no one drafted the speedy wide receiver/kick returner in 2005. Fortunately, Cribbs stuck with the Cleveland Browns as a return specialist. Cribbs has managed to return eight kicks and three punts for touchdowns during his career.

Cullen Jenkins, Philadelphia Eagles

Cullen Jenkins

After a college football career at Central Michigan, defensive lineman Cullen Jenkins latched on with the Green Bay Packers in 2003 and soon became an anchor of their defense. He left Green Bay after the 2010 season and is now a key to the Philadelphia Eagles defense. With 234 tackles and 34.5 lifetime sacks, Jenkins is a dangerous pass rusher and run stopper that could play for any team.

London Fletcher, Washington Redskins

London Fletcher

After playing at tiny John Carroll college, smallish linebacker London Fletcher has established himself as a big force in the NFL during stints with St. Louis, Buffalo and now Washington. A three-time Pro Bowl player, Fletcher has never missed a game in his 14-year career, playing in 224 consecutive games. Showing no signs of slowing down, Fletcher also led the NFL in tackles in 2011 with 166.

Brian Waters, New England Patriots

Brian Waters

Not many players are drafted out of the University of North Texas, but most players aren’t as good as guard Brian Waters. After blocking for a vaunted rushing attack while playing for Kansas City (2000-2010), Waters is now helping Tom Brady’s Patriots pass all over the AFC.

Vonta Leach, Baltimore Ravens

Vonta Leach

A big, blocking fullback who didn’t make NFL Draft boards after leaving East Carolina in 2004, Vonta Leach has become one of the best in the NFL at his unappreciated position. Three men — Steve Slaton, Arian Foster and Ray Rice — have each rushed for 1,000 yards with Leach blocking for them. He’d be a valuable asset to any rushing offense.