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On the surface, they’re relatively indistinguishable. One was the defensive player of the year in 2016, the other won the award in 2017.

Both arrived via round one of the 2014 draft. Both are entering the fifth year of their rookie contracts.

Neither has gotten the long-term deal he deserves.

But there’s a difference between Raiders defensive end Khalil Mack and Rams defensive tackle Aaron Donald, when it comes to a potential training-camp holdout.

Last year, Mack showed up. Donald didn’t. And Donald’s holdout kept him from getting a fourth year of credit toward free agency. Which means that, if he does it again (specifically, if he holds out and doesn’t show up at least 30 days before the start of the regular season), he’ll still be stuck on three accrued seasons — and he wouldn’t be eligible for unrestricted free agency next year.

That means he wouldn’t necessarily receive the franchise tag in 2019. While the Rams could still use it if they want, the Rams could instead tender him at the highest restricted free agency level, which would give the Rams the right to match an offer sheet from another team and first-round compensation if they don’t.

Donald may welcome that, since someone would surely make a run at him if the compensation is only a first-round pick. And if in the end the Rams realize that the safest course would be application of the exclusive franchise tag despite Donald having only three accrued years (even with the non-exclusive franchise tag, another team may happily surrender two first-round picks), Donald would be in the same place he would have been even if he shows up.

The only downside for Donald comes from a possible injury that would impair his market value and potentially prompt the Rams to roll the dice with the RFA tender, securing his rights for 2019 by putting millions less on the table. That dynamic would/could (should) make Donald more likely to carry a holdout deep into the regular season, in order to ensure that, come 2019, he’ll be getting the exclusive franchise tender.

By rule, he can show up as late as the Tuesday after Week 10 and get credit for the contract year. While few players ever do that, the sheer volume of disgruntled players in 2018 raises the odds that one of them will.