Around the horn: Showalter said the club is considering sending catcher Welington Castillo to Trenton, N.J., on Friday for a minor league rehabilitation assignment to play seven innings for Double-A Bowie. Castillo, currently on the disabled list with a testicular injury suffered when getting hit by a deflected pitch, would accompany the team to New York and then report to Trenton. He is eligible to be activated from the DL on Saturday. … After returning home from the West Coast on Wednesday, the Nationals gave several key starters a day off Thursday. First baseman Ryan Zimmerman, third baseman Anthony Rendon and second baseman Daniel Murphy did not start for the Nats.