But there are other Minor League players from Washington's farm system who could be in the big leagues soon. Here is a list of players who are high on the list:
RHP Aaron Barrett: The reliever has been consistent all year. Barrett has an above-average swing-and-miss slider. His fastball has been clocked as high as 95 mph. Barrett currently plays for Double-A Harrisburg.
RHP Taylor Jordan: The 17th-best prospect in the organization, Jordan is arguably the best pitching prospect in the system. He started the season with Class A Potomac and is now with Harrisburg. Entering Monday's action, Jordan has a combined 1.05 ERA between the two teams.
Jordan has a power sinker and above-average changeup. What impresses Harris the most is that Jordan is a battler when all of his pitches are not working.
"[In one game], his stuff wasn't quite as crisp. He didn't have that go-to changeup when he needed it," Harris said. "He pitched his way through it and actually went seven innings without his quality stuff."
OF Eury Perez: Perez has already had two stints in the big leagues and didn't get a chance to play much. Now back with Triple-A Syracuse, the organization's seventh-best prospect has been consistent at the plate and in the outfield. He is on pace to score 100 runs this season.
"He is a viable option for us when the need arises [for the big league team]," Harris said. "He is in a good place right now and back to where he really was last year. He is swinging the bat well, plays good defense at multiple positions [in the outfield]."
LHP Robbie Ray: The 10th-best prospect in the Nationals' farm system, Ray's fastball is up to 96 mph and he is leading the Carolina League in strikeouts while pitching for Potomac. According to Harris, Ray has power to his curveball and is developing a changeup.
"He has really done well. He has a little swagger going, and that is important," Harris said. "Success breeds confidence and confidence breeds success."
LHP Sammy Solis: After recovering from Tommy John surgery, the 13th-best prospect, is now with Class A Potomac and is averaging four innings per start.
"He is throwing the ball well," Harris said.
Before the surgery, Solis was considered a quick-to-the-big-leagues-type prospect.
RHP Blake Treinen: A sinkerball pitcher, Treinen is a now a starter for Harrisburg. According to Harris, "Treinen's changeup has really come on. His curveball is good when he hits it right. His strike quality has improved throughout the year. We are really happy where he is at."
INF Zack Walters: Acquired in the Jason Marquis trade from Arizona in 2011, Walters, the 14th-best prospect in the organization, is displaying the home run power that manager Davey Johnson predicted, but he is still having a tough time hitting for average and is known to strike out often.
"It has been a work in progress," Harris said. "He is learning a lot at Triple-A. He is making some strides, offensively. The biggest part for him is understanding his approach, and he is working on regular basis with Triple-A hitting coach Troy Gingrich. It's going to be good days and bad days."