Le’Veon Bell was born in the wrong decade. The Pittsburgh Steelers running back is the best player in the NFL at his position, but he’s playing at a time when that distinction has never been less valued. On Thursday, Bell didn’t report to camp (and was under no obligation to do so), having yet to sign his franchise tender for $12.1 million. Earlier this month, negotiations between the All-Pro and the Steelers broke down without Bell signing a long-term contract after he reportedly sought $15 million per year. Assuming Bell does sign the tender, he’ll still play this season for the Steelers as the game’s highest-paid back. But the Steelers can’t resume negotiations on a long-term deal until 2018, meaning Bell will be a free agent once again.

Put another way: This could be Bell’s last season wearing black and gold. In another era, when running backs like Earl Campbell, Franco Harris and Walter Payton were the gods of the gridiron, this would be unfathomable. But in the modern NFL, any running back, regardless of his ability, may be viewed as replaceable simply because he doesn’t throw or primarily catch the football. Despite this new line of thinking, Pittsburgh could still be making a huge mistake.

Local papers have noted that Pittsburgh has won at a higher rate without Bell the past two years (11-5 including playoffs) than with him (12-7). But Bell played in five games without quarterback Ben Roethlisberger during that span, compared with just one for his backup the past two years, DeAngelo Williams, who is no longer with the team. The Steelers went 10-3, meanwhile, when Bell and Roethlisberger both played.

In addition to durability risk, the knock on running backs is that they are interchangeable –that their success is based more on a team’s offensive scheme and run blocking than any innate ability. But that doesn’t seem to be the case with Bell.

Not every running back is replaceable Difference between teams’ primary and secondary running options by yards per attempt, 2016 YARDS/ATTEMPT TEAM RB1 RB2 RB1 RB2 DIFF. CHI J. Howard J. Langford 5.2 3.2 +2.0 SF C. Hyde S. Draughn 4.6 2.7 +1.9 DAL E. Elliott A. Morris 5.1 3.5 +1.6 PIT L. Bell D. Williams 4.9 3.5 +1.4 KC S. Ware C. West 4.3 3.3 +1.0 NO M. Ingram T. Hightower 5.1 4.1 +1.0 GB T. Montgomery E. Lacy 5.9 5.1 +0.9 SD M. Gordon K. Farrow 3.9 3.2 +0.7 ATL D. Freeman T. Coleman 4.8 4.4 +0.3 DET T. Riddick Z. Zenner 3.9 3.8 +0.1 MIN J. McKinnon M. Asiata 3.4 3.3 +0.1 TEN D. Murray D. Henry 4.4 4.5 -0.1 CLE I. Crowell D. Johnson 4.8 4.9 -0.1 JAX T.J. Yeldon C. Ivory 3.6 3.8 -0.2 HOU L. Miller A. Blue 4.0 4.2 -0.2 BUF L. McCoy M. Gillislee 5.4 5.7 -0.3 BAL T. West K. Dixon 4.0 4.3 -0.3 PHI R. Mathews D. Sproles 4.3 4.7 -0.4 DEN D. Booker C.J. Anderson 3.5 4.0 -0.5 NE L. Blount D. Lewis 3.9 4.4 -0.5 NYG R. Jennings P. Perkins 3.3 4.1 -0.8 CAR J. Stewart F. Whittaker 3.8 4.7 -0.9 CIN J. Hill R. Burkhead 3.8 4.7 -0.9 WSH R. Kelley C. Thompson 4.2 5.2 -1.1 TB D. Martin J. Rodgers 2.9 4.3 -1.4 NYJ M. Forte B. Powell 3.7 5.5 -1.8 OAK L. Murray J. Richard 4.0 5.9 -1.9 RB2 is the teams’ best backup running back with at least 50 rushing attempts. Source: TruMedia

The 25-year-old averaged 4.86 yards on 261 carries last season — or 1.36 yards more than Williams averaged in 98 attempts while running behind the same offensive line. That differential was the fourth in the NFL when comparing primary ball carriers to their best backup with 50-plus carries, according to Pro-Football-Reference.com. That means Bell gained 355 more yards on his 261 carries than his backup would have, and those extra yards are worth 23 points, based on the league rate of a point every 15.4 yards from scrimmage. That was bested only by the Chicago Bears’ Jordan Howard (1.98 yards better per carry), San Francisco 49ers’ Carlos Hyde (1.90) and Cowboys rookie Ezekiel Elliott (1.55). But in those three cases, the 2016 backups — Jeremy Langford, Shaun Draughn and Alfred Morris, respectively — are nowhere near the caliber of Williams, one of only three backs since 2000 who have matched Bell’s active streak of averaging at least 4.7 yards in three consecutive seasons (minimum 100 carries). No back this century has ever done it four straight years.

If you look at the list across the league, you begin to see why an NFL front office might think twice about giving big money to a first-string running back. There were 11 teams in 2016 in which the difference in efficiency between the starter and the backup was separated by less than half a yard per attempt. What’s more, there were 16 backups who were actually more efficient in less work, perhaps because of fresher legs. And the four backs who averaged at least 1 yard more per rush than the man they were behind on the depth chart are backups again this year. That includes the best backup rusher last year, Oakland’s Jalen Richard (1.88 yards per carry more than the now-departed Latavius Murray, who was replaced by Marshawn Lynch). More mysteriously, the Jets’ Bilal Powell (5.51 per carry) is expected to back up the same starter, Matt Forte (3.73), as is Washington’s Chris Thompson (5.24) behind Rob Kelley (4.19).

Bell’s teammates, at least, seem to appreciate his value. “We need him,” star wide receiver Antonio Brown told ESPN’s Jeremy Fowler on Monday. “He’s a special piece.” But on Wednesday, prior to training camp, Brown expressed dismay on Instagram over Bell’s anticipated absence, saying the “First rule to getting better is showing Up!”

Brown was rewarded for his stellar output with a four-year, $68 million deal in February. But Bell’s best offer from the Steelers didn’t approach that, according to Tom Pelissero of the NFL Network, which is instructive in showing how much more the NFL values passing over the ground game. But Bell is arguably the team’s second-most important receiver behind Brown, too. Last year, he became the first player in NFL history to average more than 50 yards receiving per game in addition to 100 rushing yards. And his total of 157 yards from scrimmage per game was third-most in league history.

Yet despite their arguably equal importance to the team, it’s Bell who is skipping camp while he waits on his payday. Brown, meanwhile, arrived at camp on Thursday chauffeured in the backseat of a 1931 Rolls Royce.