Murphy is dealing with the issue in the same left leg where he battled a sore hamstring that sidelined him for three consecutive games earlier this month. Baker did not say whether it was Murphy's hamstring again and indicated it was elsewhere in his leg.
"You know how things kind of move around sometime," Baker said.
Washington has reason to be extra careful with Murphy because the team can ill afford to lose him for any extended period of time. He has been the Nationals' best and most productive hitter all season, entering Saturday hitting .351/.390/.622 and a career-high 20 home runs.
Jamal Collier covers the Nationals for MLB.com. Follow him on Twitter at @jamalcollier. This story was not subject to the approval of Major League Baseball or its clubs.