With Joe Ross gone to Tommy John surgery, could the Nationals delve into the trade market for a starter? (Jonathan Newton/The Washington Post)

ANAHEIM, Calif. — Starting pitching is the foundation of the Washington Nationals, and has been for half a decade. Starting pitching is the given, the priority in the draft, the one market they always seem to browse each offseason. Since 2012, no rotation in baseball has a better FIP (Fielding Independent Pitching, an adjusted ERA) than the Nationals’ 3.49. When General Manager Mike Rizzo sees a chance to add starting pitching depth — see Max Scherzer joining the super-rotation before the 2015 season — he tends to take it.

But now, with Joe Ross headed under the knife on Wednesday and several top pitching prospects long gone in offseason deals, the Nationals have less starting pitching depth than they have in recent memory. While Ross likely would not have started in the playoffs, one more injury could constitute a debilitating blow, and even without one, they still must find a fifth starter for this season and next because of Ross’s injury. So, with all that in mind, will the Nationals dive into the starting pitching market at this year’s trade deadline? If they do, who might they consider? If they don’t, who will fill the void?

First of all, the Nationals do not have a history of making deadline deals for big-name (or even little-name) starters. They’ve added rentals to fill holes, such as Asdrubal Cabrera or Mark Melancon, but have never engaged in one of those future-altering megadeals involving a big-time starter during the season. Though top-tier starters such as Sonny Gray and Justin Verlander are reportedly available, the Nationals almost certainly will not take a look at either.

Less-heralded rentals could also be available, veterans such as Clayton Richard or Trevor Cahill (or most of the San Diego rotation), or perhaps even Blue Jays starters such as Marco Estrada or Francisco Liriano — among many others. But the Nationals are unlikely to make much of a push at starters from either group. Adding a starter is low on their list of priorities, according to one person familiar with their mind-set. Bolstering the bullpen remains a focus.

So unless someone makes one of those offers they can’t refuse, the Nationals seem likely to turn to internal options to fill their fifth starter’s void, at least for now. The first man to audition will be 33-year-old Edwin Jackson, who returns to the Nationals for the first time since 2012 to start against the Angels on Tuesday night. If Jackson can find his way — and his one run allowed in 20 1/3 innings at Class AAA Syracuse is certainly encouraging — he will get every opportunity to stick. Jacob Turner could do the same.

Familiar homegrown options have been less promising. A.J. Cole is pitching to a 1.71 WHIP and .325 batting average against for the Chiefs this season. Austin Voth has battled injuries to a 1-7 record and 6.38 ERA, all of which contributed to his demotion to Class AA Harrisburg yesterday. Sean O’Sullivan, who has 56 major league starts to his name, has a 4.40 ERA in eight games at Syracuse.

Erick Fedde, meanwhile, has only built back up to 3 2/3 innings since his brief relief immersion, and might therefore need a few more weeks to be ready. While he could serve as Ross’s replacement next season — Max Scherzer, Stephen Strasburg, Gio Gonzalez, and Tanner Roark will all be back — he does not seem likely to be ready to replace him right away, should Jackson falter Tuesday.

Some of those starters on the market will likely remain so in the winter, and the free agent class will include Jake Arrieta, Yu Darvish, and other big names. If they feel a need, the Nationals can add then.

But for now, the Nationals will bet on their guys to fill out what remains a sturdy rotation if healthy, but is nevertheless in a more precarious spot than usual if not.

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