"It means a lot," Difo said. "I know now that I’m here it’ll open the doors for the other guys."
The 6-foot-4, 210-pound, size-16-shoe infielder is only 20 years old.
Zimmerman's yearly charity event at Nationals Park will be held on June 22.
Elbow, back and shoulder injuries slowed the left-hander's ascent to the majors, but Solis looked good in relief on Thursday night.
The Nationals 23-year-old pitching prospect had a tough first outing, but says he will learn from the experience, not dwell on it.
With Matt Grace making his debut, the 2013 Senators have sent 15 players to the major leagues.
The Suns and P-Nats endured an improbable Wednesday, as both were no-hit and one of them won.
The 2014 first-round pick threw his first bullpen recently and is pleased with progress so far.
Several Nationals minor league coaches knew Robinson from the Kansas City system and spoke highly of him.
Neither pitching prospect is hurt, the Nationals say; they're just under a delayed throwing program.