Gio Gonzalez spent all day Thursday trying to get back to Washington after the all-star break, and he is pitching a day later than scheduled as a result.
The left-handed starter's fastball was down one to two miles per hour from normal, and he still threw well.
Bryce Harper swung a bat with both hands Tuesday, but his ensuing return probably won't lead to a shakeup.
The outfielder first felt the back discomfort Sunday morning and considers it minor.
The left-handed reliever will be with the Nationals for, at least, the weekend as an extra arm in the bullpen.
The left-handed pitcher's command was improved in his second rehab start, allowing only one run on two hits but walking four.
Gio Gonzalez hoped to return to the Nationals this week in San Francisco, but he'll have to wait after a bad rehab start.
The left-handed starter is unsure if he will rejoin the Nationals rotation next or make another rehab start.
Gonzalez is expected to make one rehab start for Class A Potomac and then re-join the Nationals if there are no issues.
The left-handed starter faced four teammates and simulated three innings on Sunday morning.