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The Washington Nationals have lost their top remaining trade chip to a season-ending injury. 

Righty reliever Kelvin Herrera was placed on the 10-day DL on Monday with a torn Lisfranc ligament in his left foot, the team announced. Lisfranc tears can take months to heal depending on the severity.

Herrera suffered the injury Sunday while fielding a ground ball in a blowout. He had to be carted off the field. Here's the video:

Sunday's outing was Herrera's second back from a two-week stint on the disabled list for an unrelated shoulder injury.

The Nationals acquired Herrera from the Royals for three prospects back in June, when they still in the postseason race. He was automatic in Kansas City, throwing 25 2/3 innings with a 1.05 ERA and a 0.82 WHIP. With Washington, Herrera had a 4.34 ERA in 18 2/3 innings overall.

Herrera is an impending free agent and it stood to reason the Nationals would look to trade him before the August 31 postseason-eligibility deadline. Bullpen help is always in demand and Herrera's track record is about as good as it gets. Instead, the injury means Washington won't be able to move him the way they moved Daniel Murphy and Matt Adams last week.

For Herrera, the injury comes at a bad time because he is an impending free agent, and the injury figures to cut into his earning potential. Free agency was not kind to players last winter, though relievers were still paid very well, and I suspect Herrera will get a significant contract despite the foot injury. Just not as significant as he would've gotten if healthy.