Report: Nationals keeping close eye on Royals' Herrera

Another day, another reliever linked to the inconsistent Washington Nationals bullpen.

The club is keeping a close eye on Kansas City Royals closer Kelvin Herrera, according to Bob Nightengale of USA Today Sports.

The Nationals' reported interest in Herrera is nothing new, as FOX Sports' Ken Rosenthal linked the club and the hard-throwing reliever in early May.

Herrera would provide a decent boost in the back end of Washington's bullpen, which has combined to post an alarming 5.05 ERA this year - second-worst in the league.

The Nationals, whose search for upgrades will likely continue ahead of the July 31 trade deadline, have shuffled their closer position multiple times this year, rotating between Blake Treinen, Shawn Kelley, and Koda Glover.

Once heralded for his clutch performance out of the pen, Herrera has struggled this season with the Royals. While his 4-24 walk-to-strikeout ratio is solid, he's posted the worst ERA (4.30) of his career, and an equally poor FIP (4.88). He's also surrendered six home runs in only 23 innings.

He'll earn $5.35 million this year and qualify for arbitration in 2018, with his first year of free-agent eligibility slated for 2019, barring an extension.