It's not that the Eagles have a vast store of backup linemen. In fact, the main critique of the club's offensive line is that it lacks viable depth.
But if the Eagles had to lose anyone, really, Johnson was the best man for the job.
Because he isn't very good at his job.
Not yet, anyway.
Johnson, a first-round pick in 2013, has started 28 games at right tackle in his life. He was drafted for his athleticism, not his technique; he played quarterback, then tight end, then defensive end in college. He has played a total of 41 football games on the offensive line. The learning curve for him is nowhere near its crest.
The main reason why tight end Brent Celek's offensive output has dwindled the past two seasons? He spent too much time babysitting two guys who had never played right tackle in the NFL.
One of those guys, Dennis Kelly, managed to figure out the position by the end of 2012. However, Kelly hurt his back in training camp last year and has been unavailable since.
Kelly's fitness probably is less important, considering the Eagles seem to prefer athletic guard/tackle Allen Barbre, anyway. He's a seventh-year player who spent last season with them after a PED suspension ended his association with the Seahawks in 2012. They signed Barbre to a 3-year extension in June. Barbre could slide into the right-tackle spot, where his only NFL starts have come (seven, in Green Bay, in 2009) or he could play right guard and move Todd Herremans back to tackle, where Herremans played in 2011 and part of 2012.
Again . . . not so you'd notice.
That might sound illogical, since the best unit on the team last year was the offensive line, and will be so again this season. Johnson, however, is almost coincidental to that reality.
The line needed the first half of last season to allow left tackle Jason Peters to overcome a twice-ruptured Achilles' tendon; center Jason Kelce, a knee injury; and Herremans, a foot injury, and the change from right tackle to right guard. The entire line needed to learn Chip Kelly's offensive scheme and its pace. Peters and Herremans had to adjust to a third line coach in 4 years.
By the time they jelled at midseason, Johnson, the rookie, was able to just follow their wake.
If the unit lost anyone else, it would be disastrous: Kelce, the leader; Peters, someday a Hall of Famer; Herremans, who has played three positions; Evan Mathis, the most respected left guard in the league.
If any of the other units lost a starter, it would resonate more.
Nick Foles, of course, is the most irreplaceable, considering his mastery of the offense and the bizarre collection of understudy quarterbacks behind him.
LeSean McCoy is right behind, considering he is the most talented player on the team and possibly the best back in the league.
Celek's blocking skills are nearly irreplaceable and, if allowed, he can be a devilish receiver and runner, but Zach Ertz was a second-round pick and James Casey a touted free-agent addition last season. This one's closer, but there would be a dropoff.
The Eagles already chose to gamble at the receiver position . . . but, until rookies Jordan Matthews and Josh Huff actually catch a pass in an NFL game, unremarkable Riley Cooper and bionic Jeremy Maclin are invaluable.
Things are more nebulous on the defense, simply because it lacks playmakers.
Of course, the loss of outside linebacker Connor Barwin would be massive, as would that of inside linebacker DeMeco Ryans, if only because they seemed to never leave the field. Even converted defensive end Trent Cole began to flash at linebacker as last season progressed, and inside 'backer Mychal Kendricks seems ready to explode.
Cornerbacks Bradley Fletcher and Cary Williams have no ready replacements, and that includes nickel corner Brandon Boykin, whose lack of size will always hurt him on the outside. Fourth-round rookie Jaylen Watkins? Reread that stuff about the wideout position.
The Eagles made their only meaningful full-time upgrade at the safety position when they acquired Malcolm Jenkins. Lose him and try to cobble together a defensive backfield of Nate Allen, Earl Wolff and fifth-rounder Ed Reynolds. The defense would be playing so soft, it might never record another sack.
They have defensive ends enough, but none is good enough to afford the loss of any. None, really, is the right profile for the position, so all have to play a lot to make the defense decent.
Which brings us to the nose guard spot.
Of all places.
Who can replace Bennie Logan? Undersized Damion Square? Seventh-rounder Beau Allen?
The Eagles would be better off feeding Lane Johnson some more of that sports science stuff, let him learn yet another position, then cross their fingers when the testers come to call.
On Twitter: @inkstainedretch