Nunez will start at shortstop and bat ninth in Wednesday's game against the Diamondbacks.
A Rule 5 selection, Nunez has been on the Nationals' active roster all season but has seen little playing time, as Washington presumably doesn't view the 23-year-old as being major-league ready but still values him as a developmental piece. Nunez, who will make his third start of the season Wednesday, has logged just eight plate appearances and is still looking for his first MLB hit.