The Washington Nationals are off to a good start. They entered Thursday 25-14 with a National League-best eight-game division lead. Barring a slew of injuries or coinciding slumps, it seems likely the Nationals are secure in their standing as a playoff lock.

Yet if the Nationals are likely to lose sleep about something, it's  probably the same one they appeared to have entering the season: the bullpen. Predictably, perhaps, Washington general manager Mike Rizzo has started calling around looking for upgrades -- specifically with regards to the ninth inning, according to Jon Heyman of FanRag Sports:

They have spoken internally about many possibilities, though, including Kansas City Royals closer Kelvin Herrera, Tampa Bay Rays closer Alex Colome, San Francisco Giants closer Mark Melancon, Miami Marlins closer A.J. Ramos, and Toronto Blue Jays closer Roberto Osuna.

Heyman notes that White Sox closer David Robertson "perhaps makes the most sense." Robertson has been connected to the Nationals in rumors before for obvious reasons: he's a closer on a rebuilding team who has another year remaining on his contract (he'll receive $13 million in 2018). 

For his part, Robertson seems unmoved by the trade talk. In 13 appearances he's managed a 3.21 ERA with a 3.33 strikeout-to-walk ratio. He's also converted five saves in six tries. 

The Nationals have had six pitchers earn saves, including Blake Treinen and Shawn Kelley, each of whom has an ERA over 7.00.