ASHBURN, Virginia -- The Washington Redskins rarely mention Trent Williams' name without including this description: He's the best left tackle in football. Whether others in the NFL agree or not doesn't matter. That's their opinion.

So keeping him around until he retires should be a no-brainer. But it's tougher than you might think for several reasons. And it has nothing to do with his talent.

It also involves how long of an extension Williams wants -- his current deal expires after the 2020 season. Washington has an excellent cap strategist in Eric Schaffer, who has been adept at crafting deals that make sense for both sides.

Williams has plenty on his side to justify wanting a new deal, starting with the fact that he is allowed to want one. Who doesn't? He can see what other NFL tackles are signing for, knowing he's better -- and knowing his next big payday would come in 2021 and it might not be as good as it would be right now. Time could be ticking on his leverage. One note: The Redskins did make him the highest-paid tackle in 2015. This isn't a matter of not "paying the man."

They do not have a clear succession plan at this point; they also didn't have one when they dealt with this a decade ago when Chris Samuels was nearing the end of a successful run in 2009. A year later they drafted Williams with the fifth overall pick.

But, as one front-office executive from another team said, Williams has the Redskins by the, ahem, groin area. At this point, the Redskins' tackle depth is questionable. Last year's third-round pick, Geron Christian, struggled as a rookie and still can't participate as he recovers from MCL surgery on his right knee. They signed Ereck Flowers to compete at left guard, but for now he's also their swing tackle. Flowers has struggled in the NFL. The Redskins have a rookie quarterback in Dwayne Haskins who will play at some point this season; they want (or, need) Williams on the field to protect this pocket passer.

Keep in mind, though, that these aren't necessarily the players who would replace Williams if the Redskins make him play on his current deal. If Williams plays and stays healthy, depth isn't an issue. If he doesn't show up for training camp? Then, yeah, there would be trouble. But the Redskins' leverage is this: Since he's signed through 2020, they can always use the franchise tag if needed in 2021 -- assuming he doesn't sit out and demand a trade.

Williams has made seven Pro Bowls, an award that can sometimes be dismissed as a popularity vote (he has never made first-team All-Pro). But Williams' play warrants postseason recognition. The Redskins can run plays that stretch the field in a different way because of his speed to first block inside, then sprint outside for another block on a screen, for example. He does things that often make you say, "No other tackle could do that."

However ... Williams turns 31 in July and hasn't played a full season since 2013. He has missed a combined 13 games the past three years, though four stem from a suspension for taking a banned substance. The NFL has banned him twice.

Williams has fought through more health issues than most players, grimacing after games as he leaves the stadium because of the pain. He battles. He keeps playing until his team has been eliminated, knowing what he means to the offense. Several times the smart thing for him -- and what could possibly extend his career -- was to shut it down and have surgery. He kept playing.

People in the organization acknowledge the dilemma. They need him; they know how good he is -- but they also are well aware of the injury history. If they give him three more years, how healthy will he be at age 35? That's impossible to answer for any player, of course, but every contract must acknowledge and mitigate that risk.

If Williams were a free agent from another team, the Redskins would pass. They have stayed away from signing over-30 players with injury histories. But Williams is one of their own and has meant a lot to the franchise. The Redskins can't afford to see him play somewhere else, but the question is clear: How long can they afford to keep him around?