COLUMBIA — When college football recruits sign their letters of intent on Wednesday, South Carolina will secure probably its best group of offensive linemen in coach Steve Spurrier’s nine recruiting classes.

South Carolina’s offensive line commitments for the Class of 2013. All rankings from

Na’Ty Rodgers (6-5, 278) – No. 15 tackle, No. 6 in Maryland, No. 181 nationally

*D.J. Park (6-6, 335) – No. 19 tackle, No. 4 in South Carolina, No. 220 nationally

Bryce King (6-4, 300) – No. 3 center, No. 5 in South Carolina

Alan Knott (6-5, 275) – No. 53 tackle, No. 65 in Georgia

J.P. Vonashek (6-6, 255) – No. 54 tackle, No. 61 in Georgia

*Enrolled in January and will participate in spring practices.

But will they become productive players? Regardless of how positive a coach spins at his press conference, that is the unanswerable question on every National Signing Day. Recruiting is an inexact science, and perhaps no position is tougher to evaluate than offensive line.

It is obviously critical for any offense that wants to succeed, especially in the Southeastern Conference, where fearsome defensive lines are the norm.

Under Spurrier, USC has had uneven results in offensive line recruiting. Partly because of this, the Gamecocks’ offense has sputtered at times. While they finished 11-2 in 2011 and 2012, they ranked 73rd and 84th nationally in yards per game. They allowed 30 sacks in 2011 and 38 last season, No. 85 and 110 nationally.

There are mitigating factors. South Carolina’s best offensive player, running back Marcus Lattimore, missed 10 combined games the past two seasons because of knee injuries. And it is shortsighted to blame an offensive line for every sack allowed.

Still, Spurrier made no secret last season about his frustration with his line’s inconsistent performances, though the group improved later in the year.

Spurrier has two highly rated linemen in this class — Maryland’s Na’Ty Rodgers and Dillon High’s D.J. Park, who are rated the No. 15 and 19 tackles by, and the No. 181 and 220 overall recruits. Bryce King, Park’s high school teammate, is rated the No. 3 center.

Two of USC’s recent top line recruits have worked out reasonably well so far. Goose Creek’s Brandon Shell started as a redshirt freshman right tackle last season. He was the No. 4 tackle and No. 66 overall recruit in 2011. A.J. Cann last year was a third-year sophomore in his second season starting at left guard, after being the No. 2 center and No. 182 overall recruit in 2010.

But for every Shell and Cann, there are players like Quintin Richardson, the No. 8 tackle in 2007, who never significantly contributed in three seasons and transferred to lower-division Hampton. Or Tramell Williams, the No. 9 center in 2010, who redshirted that year, then transferred. Or Kevin Young, the No. 20 tackle in 2006, plagued by injuries at USC and never a factor.

USC isn’t alone. Just look at Rivals’ offensive tackle rankings in 2007. The top three are Josh Oglesby (Wisconsin), Ryan Miller (Colorado) and Matt Romine (Notre Dame). Ever heard of them? Probably not. They had uneventful college careers, for various reasons.

But at No. 6 is Bryan Bulaga (Iowa), a first-round pick by the Green Bay Packers in 2010 — a testament to the riches available if you prove you can play this valuable position as well as everybody thought you could when you were 18 years old.

Size, smarts not guaranteed

That is a substantial “if” for several reasons. Certainly, the high potential for injuries on the line, where collisions are the closest and most frequent, makes it difficult to project long-term success out of high school. There are other factors, such as physical growth, mental acumen and the willingness to embrace a thankless existence of physical punishment.

“Offensive linemen are the hardest guys, I think, to evaluate,” said Goose Creek coach Chuck Reedy, a former longtime college assistant coach, including 1978-89 at Clemson. “There are a lot of intangibles that make them more difficult to evaluate than other positions.”

Before college assistants worry about whether a kid is smart enough to play offensive line in the SEC, they must consider one thing above all else — size. Few linemen emerge from high school large enough, which is why most redshirt. College coaches have to look at a kid and determine whether he can pack on 30 pounds, keep it on during the season and still move nimbly.

“It’s the hardest position to figure because you can’t really tell what their developmental process is,” said Dillon coach Jackie Hayes. “You’ll see a lot of big kids that play, but their coordination is not where it needs to be. Sometimes, you go out on a limb, and hopefully you can develop that.”

Shell, who is 6-6, now weighs 330 pounds. In the fall of 2010, as a high school senior, he was 290. Reedy said Shell’s frame indicated he could add weight. But high school tackles who are 6-4 and 270 pounds “are the ones that sometimes you have a hard time projecting,” Reedy said.

Everyone knows you need more than size to play college offensive line. High schools use about three to four blocking schemes, half as many as colleges, said Hayes. Defensive fronts are more complex and disguised in college, so “you’ve got to be able to instinctively react to what you’re seeing,” Reedy said.

College coaches usually gauge a recruit’s intelligence by asking about his grades. But Goose Creek and other high schools around the state are now using a computer program that could help recruiters better determine a kid’s commitment to learning football. It’s called Hudl, and it lets players access their team’s film database from home. Coaches can see when players log in, so they know who is putting in extra work.

Telltale sign of potential?

Even if a recruiter knows a lineman is big and watches film, analyzing his games can be difficult. Many high schools, like Goose Creek, still use run-focused offenses that require little pass blocking. The spread offense is becoming more popular at places like Dillon, but because it uses quick passes, a tackle doesn’t have to hold off a defensive end for long. And of an elite lineman’s hours of game action, many are against defensive linemen who are much lighter.

“You don’t get to see them display their skills the way you do skill (position) guys,” Reedy said. “A skill player, you’re going to see their speed. You’re going to see them catch the ball. If it’s a defensive guy, you’re going to see how loose their hips are, how they backpedal. A quarterback, you can see him throw. A lot of times, the level of competition doesn’t factor in with those (skill) guys because the skills they have are the skills they have.”

Mike Farrell, Rivals’ national recruiting analyst, believes there is one trait that shows up on an offensive lineman’s game film, regardless of the system or opponent. And it is a must-have in college — aggression. For that reason, Farrell doesn’t find offensive linemen as difficult to analyze as cornerbacks, because they never get thrown at, and quarterbacks, because so much of that position is mental.

Farrell still remembers the film of guard Andre Smith, who went to Alabama and was the sixth overall pick in 2009. Smith had a sloppy-looking body, but Rivals rated him the No. 2 overall recruit in 2006 largely because of what Farrell noticed about Smith’s attitude.

“This kid was blocking kids into the first row,” Farrell said. “And you’re like, ‘Oh, my gosh, this kid’s an animal. He’s going to be super successful. He just wants to put you in the bleachers.’ That’s the only way you can tell if a kid has it or doesn’t: How does he respond to getting popped in the face?

“I don’t care who you’re playing against. As long as you put him on his butt every play, that shows me something. I think physicality comes out on film pretty quickly, and I think it’s the most important factor by far, especially with these freaks on the defensive line. You better be willing to hit that guy as hard as you can.”

For that reason, Farrell is hopeful about Rodgers, USC’s top-rated tackle for 2013. Yes, Rodgers tends to hold defensive ends, a flaw USC’s coaches can fix, Farrell said. But he will come to Columbia with something that is harder to teach, something Farrell saw at a camp when Rodgers was knocked down and had his lip bloodied, only to come back and play angrier than before.

“He’s a kid they don’t really have to worry about, the first time he gets hit, going home and crying,” Farrell said.

South Carolina Top-20 and National Top-50 Recruiting Lists

South Carolina Top 20

Player, High School Pos. Height Weight College

1. Michael Hill, Pendleton DT 6-3 315 Ohio State

2. Mike Williams, Lake Marion WR 6-4 185 Clemson

3. Tramel Terry, Goose Creek ATH 6-0 190 Georgia

4. D.J. Park, Dillion OL 6-6 335 South Carolina

5. Bryce King, Dillon OL 6-4 300 South Carolina

6. Gerald Turner, Goose Creek LB 6-1 255 South Carolina

7. Justin Evans, Wilson OL 6-6 275 S.C. State

8. Jabo Lee, Dillon RB 5-10 180 East Carolina

9. Jabar Johnson, Orangeburg-Wilkinson ATH 6-1 180 Clemson

10. Ben Boulware, T.L. Hanna LB 6-0 225 Clemson

11. Chocolate Wilson, Myrtle Beach DB 5-9 160 Marshall

12. Marcus Edmond, Lower Richland ATH 6-1 175 Clemson

13. Jaylen Miller, Gaffney DE 6-3 265 Undecided

14. Mykal Moody, Conway ATH 5-11 180 Undecided

15. Jalen Stevens, Goose Creek DE 6-4 220 UConn

16. Harold Atkinson, Carolina Forest RB 6-1 210 S.C. State

17. Justin Day, South Aiken OL 6-8 285 Kentucky

18. Taylor Chambers, Irmo OL 6-7 285 Wake Forest

19. Gabe Brander, Heathwood Hall OL 6-4 250 Duke

20. Justin Bridges-Thompson, Spartanburg DB 6-2 195 Charlotte

National Top 50

Player Hometown Pos. Height Weight College

1. Robert Nkemdiche Loganville, Ga. DE 6-5 270 Mississippi, LSU

2. Vernon Hargreaves Tampa, Fla. DB 5-11 185 Florida

3. Jaylon Smith Fort Wayne, Ind. LB 6-3 215 Notre Dame

4. Carl Lawson Alpharetta, Ga. DE 6-2 255 Auburn

5. Laquon Tredwell Crete, Ill. WR 6-3 200 Mississippi

6. Keeny Begelow Elkton, Md. DT 6-3 295 Southern Cal

7. Max Browne Sammamish, Wash. QB 6-5 215 Southern Cal

8. Derrick Green Richmond, Va. RB 6-0 220 Michigan

9. Kendall Fuller Olney, Md. DB 5-11 190 Va. Tech

10. Jalen Ramsey Nashville, Tenn. DB 6-0 190 Southern Cal

11. Jonathan Allen Ashburn, Va. DE 6-3 255 Alabama

12. Su’a Cravens Murrieta, Calif. DB 6-1 205 Southern Cal

13. Reuben Foster Auburn, Ala. LB 6-2 230 Georgia, Auburn, Ala.

14. Laremy Tunsil Lake City, Fla. OL 6-6 295 Ala., Georgia, Mississippi

15. Matthew Thomas Miami LB 6-3 205 Alabama, FSU, Georgia

16. O.J. Howard Autauga, Ala. TE 6-6 220 Alabama

17. Thomas Tyner Beaverton, Ore. RB 6-0 200 Oregon

18. Tre’Davious White Shreveport, La. DB 5-11 175 LSU

19. Greg Bryant Delray Beach, Fla. RB 5-11 200 Notre Dame

20. Chris Jones Houston DE 6-5 250 Mississippi State

21. Eddie Vanderdoes Placer, Calif. DT 6-3 310 Southern Cal, UCLA

22. Leon McQuay Seffner, Fla. DB 6-2 185 Southern Cal

23. Frank Herron Memphis, Tenn. DE 6-5 260 LSU

24. Christian Hackenberg Fork Union, Va. QB 6-4 210 Penn State

25. Montravius Adams Vienna, Ga. DT 6-3 290 Georgia, Ala., Clemson

26. Mike Mitchell Plano, Texas LB 6-4 215 Ohio State

27. Ty Isaac Joliet, Ill. RB 6-3 215 Southern Cal

28. Alex Anzalone Wyomissing, Pa. LB 6-3 215 Florida

29. Taquan Mizzell Virginia Beach, Va. RB 5-10 185 Virginia

30. Max Redfield Mission Viejo, Calif. DB 6-2 195 Notre Dame

31. Dorian Johnson Belle Vernon, Pa. OL 6-6 280 Pittsburgh

32. Von Bell Rossville, Ga. DB 6-1 190 Ala., Ohio St., Tennessee

33. A’Shawn Robinson Fort Worth, Texas DT 6-5 305 Texas

34. Chris Hawkins Rancho Cucamonga, Calif. DB 5-11 170 Southern Cal

35. Jalin Marshall Middletown, Ohio ATH 5-11 200 Ohio State

36. Derrick Henry Yulee, Fla. RB 6-3 245 Alabama

37. Marquez North Charlotte WR 6-3 205 Tennessee

38. Kelvin Taylor Belle Glade, Fla. RB 5-11 215 Florida

39. Cameron Burrows Tretwood, Ohio DB 6-0 205 Ohio State

40. Ricky Seals-Jones Sealy, Texas ATH 6-5 220 Texas A&M

41. Kent Perkins Dallas OL 6-5 300 Texas

42. Mackensie Alexander Immokalee, Fla. DB 5-11 175 Texas A&M, Rutgers

43. Derrick Griffin Rosenberg, Texas WR 6-6 215 Texas A&M

44. Tray Matthews Newnan, Ga. DB 6-0 195 Georgia

45. Alvin Kamara Norcross, Ga. RB 5-10 190 Alabama, Georgia

46. Robert Foster Monaca, Pa. WR 6-3 170 Alabama

47. Joey Bosa Ft. Lauderdale, Fla. DE 6-5 270 Ohio State

48. Keith Ford Cypress, Texas RB 5-11 195 Oklahoma

49. Al-Quadin Muhammad Ramsey, NJ DE 6-4 225 Miami

50. Ethan Pocic Lemont, Ill. OL 6-7 285 LSU