Every draft class has one, the collegiate superstar quarterback with little chance of making an impact in the NFL. His name has been Collin Klein and Kellen Moore, Tim Tebow and Troy Smith, Jason White and Danny Wuerffel and Andre Ware. They all play hard, look you in the eye, call you "sir," rally the troops when down by six in the fourth quarter. But most are a little too small, too weak-armed, too scattershot or too customized for college strategies to become starters at the next level. The fans in the student section cannot see it. The SportsCenter highlights do not detect it. But the scouts and opposing defenses pick it apart.

This year, the falling star is named Tajh Boyd.

Boyd was Clemson's starting quarterback for three seasons. He amassed 11,904 passing yards, 107 touchdowns with just 39 interceptions and a 64.3 percent completion rate that improved every single year. He also ran for 1,165 yards and 26 touchdowns. He led the Tigers to two Orange Bowls, winning one of them. He helped beat LSU in the 2012 Chick-fil-A Bowl, throwing for 346 yards and two touchdowns in a come-from-behind 25-24 victory. His college career was marvelous. He was a thrill to watch. He is a wonderful young man to interview.

He will not be a quality NFL starter. And it is hard to tell at this point if he will even be drafted.

Falling by degrees. Boyd took the field for Clemson's pro day in shorts and a compression T-shirt on Thursday. He threw passes to Sammy Watkins and his other receivers. It was a loose non-dress rehearsal like any other pro day, a game of pitch-and-catch in a quiet indoor practice facility. Boyd did not appear to be under any sort of pressure, but there was a lot at stake.

Pro days are supposed to be easy for quarterbacks. The drills and throws are tightly scripted, and the quarterback's favorite receivers are on hand to catch his throws. You are familiar with the silly trope of publishing pro day completion percentages: Prospect X was 39-of-40, and his only incompletion was dropped! The fact is that quarterbacks should complete almost 100 percent of their pro day passes. The drills are supposed to be easy.

Many things looked easy for Boyd on Thursday. And he completed a lot of passes: 63 of 64, according to those who cared to count them. He looked comfortable throwing with a newly ironed-out delivery, courtesy one of those passing academies that run a quarterback's throwing motion through motion sensors and calipers.

But he also forced one receiver to dive for a sideline pass, and he led Martavis Bryant so far on another sideline pass that Bryant slammed into a television camera. Receivers had to speed up or throttle down to line up with his deeper throws. This was with no pass rush, no defense to read and the only pressure coming from the eyes of scouts trying to determine just how big an issue Boyd's accuracy might be at the NFL level.

The pro day was no disaster, but it did not provide many answers. The scouting combine was no disaster, either, but it raised questions.

Boyd took the podium in Indianapolis last month like a classic falling-star quarterback, begging his case to a sympathetic press pool. "I mean, coming into the season, I was a top-15 pick, supposedly. Now you're hearing this and that. I think it switches that quickly. And nobody really knows until May, so I'm just trying to go out here and do what I can."

True to falling-star form, Boyd stood on his record when asked about his greatest attribute as a quarterback. "Ultimately, man, I just feel like I win games: 32-8 at Clemson, was 43-2 in high school. I mean, winning's just something I've always been a part of."

A quarterback citing his collegiate win-loss record is almost always a prospect in jeopardy. All of these guys won in college, or we would not be writing about them; they all won in high school, or else they would not have reached a major football college. Six-foot-five cannoneers and 4.5-running gazelles never have to explain what their greatest attribute is. Boyd sounded confident, and just a little defiant, as falling stars are supposed to.

But then drill results came in. Boyd measured just below 6-foot-1. His 40-yard dash lasted 4.84 seconds. His passing drills were a hit-or-miss affair, with Boyd over-striding and placing short passes poorly.

Yes, Russell Wilson is short. And every Wonka Bar wrapper may contain a golden ticket. Wilson was three-tenths of a second faster in the sprint and completed accurate passes effortlessly against air. Boyd is short, not-so-fast, a little lumpy and, as both his pro day and the combine showed, erratic even under ideal conditions.

Clemson's pro day and the combine were continuations of a free fall that was already underway at the Senior Bowl. Boyd was not terrible in Mobile, though much was made about an anonymous scout calling him "undraftable." Boyd was wild on passes over the middle and did not look comfortable reading the field from the pocket, though his velocity was pretty good, his mobility was fine and his poise did not waiver. It was a fourth-rounder's performance.

The fall started with Clemson's 51-14 loss to Florida State last October, when Boyd completed just 17 of 37 passes for 156 yards, one touchdown, two interceptions and a fumble. The final score was only a small part of the problem, the passing stats a slightly larger one. It was the circumstances. Florida State was one of the few teams whose defense could stand up to Boyd's all-conference receiving corps. For one rare evening, Boyd did not have wide-open receivers to throw to or easy screen-and-run opportunities for 40-yard gains. He faltered badly, and it happened at just about the time when those of us who anoint "top-15 picks" a year in advance -- those of us with articles to write and zero real dollars on the line -- start to get serious about looking at the best college prospects.

Boyd began falling that evening, and he kept falling through Thursday, and there is little he can do to stop it. Boyd cannot get taller, can get only a heartbeat faster, and while he can keep smoothing hitches in his delivery, he cannot erase two years of scouting tape.

Over supported. Watch Tajh Boyd like a scout, and you come away impressed with Sammy Watkins.

Watkins breaks wide open up the seam, and Boyd connects with the easy-to-spot target for a big gain. Watkins hauls in a screen, sometimes reaching or scooping the short pass, and great things happen. Watkins runs a slant into the front of the end zone, and he does not let the fact that Boyd's pass arrives behind his back shoulder prevent him from angling backward to preserve a touchdown.

After enjoying Watkins for a while, you notice Martavis Bryant: tall, smooth and able to glide past defenders and defenses wary of Watkins. If you are watching 2012 tape, DeAndre Hopkins leaps off the screen the way he now leaps over defenders for the Houston Texans.

What you notice once you watch the Clemson offense analytically is how customized the scheme is for the talents of Watkins and Hopkins-then-Bryant. Watkins is the queen of the chessboard. He is Sterling Sharpe during his Packers prime. Watkins starts in the backfield, or motions to the right, and the entire defense goes on amber alert. If he stands in the right flat for a screen while Bryant runs a vertical route up the left sideline, the other Clemson receivers might as well be covered by the opponent's mathlete team. Whole Clemson play concepts are designed around Watkins feigning to the left while Boyd rolls right to choose from a sampler platter of overlooked receivers. The Clemson offense looks at times like it was designed by a middle-school coach who suddenly acquired a 17-year-old who was held back a few times.

As for Boyd, he took to the weapon-saturated scheme like a bright, experienced quarterback should. He sells his fakes and delivers those screens. He finds those secondary receivers hiding in plain sight. He runs keepers and options into the hearts of strained defenses, squirting though holes and diving for first downs. He also sometimes bounced passes to receivers a dozen yards away, makes Watkins and Bryant work for those screens and places what should be easy throws at the knees or behind the back shoulder. And when pressure arrives, which is not all that often, Boyd becomes erratic.

At his best, Boyd was B.J. Armstrong distributing the ball to Jordan and Pippen. Or he was 2013 Andy Dalton, propped up on phone books behind the wheel of a muscle car.

Dalton is an interesting comparison. He has had some NFL success. Boyd is a smaller, quicker, less accurate Dalton. Give him great receivers and the proper scheme and he can squeak into the playoffs. But that can be said of many, many quarterbacks. Where would you draft a college quarterback likely to max out as Andy Dalton? Perhaps the third round. Perhaps the seventh. Maybe never. Certainly not in the top 15.

True value. Boyd's best NFL opportunity may come as a designated backup. The Packers need someone who can soak up games when Aaron Rodgers is unavailable. The Cowboys could use an affordable understudy to Tony Romo. Russell Wilson's lone backup right now is B.J. Daniels. Career backups have different skillsets than top prospects. They need ever-ready work habits and a spark-plug playing style. Boyd has both. He can take his name off the free fall list and put him on another list, one that includes Shaun Hill, Bruce Gradkowski, Josh McCown and Seneca Wallace: professional middle relievers who can hang around the NFL for a decade. Boyd can emerge a winner after all.

For now, he must cope with a free fall that is more about perception than reality. Boyd is not plummeting, just course-correcting. He would not have been a first-round pick if he had left college in 2012. He will not be a first round pick this season. If he is a Russell Wilson fairy tale, the lady with the wand had better turn up fast.

Boyd is not "undraftable" either. The Senior Bowl, his pro day and the combine keep pointing in the same direction: toward Day Three of the draft, the chance to give a coach a firm handshake and stake out a career as a spot starter and pepperpot. He could have Andy Dalton playoff runs in a Maserati offense and/or a dignified McCown late career. It's all about expectation management: his, his team's and ours. Boyd can emerge from his free fall as a useful, well-compensated NFL player. He just has to land on his feet.