WASHINGTON -- The Nationals activated infielder Aaron Boone from the disabled list on Thursday and placed shortstop Alberto Gonzalez on the 15-day DL, retroactive to August 5, with a left hamstring strain.

Boone missed the past 30 games after suffering a left calf strain on July 6 against the Reds. He went a combined 2-for-11 with a double in four games during rehab stints with the Nationals' Gulf Coast League affiliate and Triple-A Columbus. The 35-year-old Boone was hitting .258 with five home runs and 17 RBIs before the injury.

Gonzalez, 25, was hitting .462 (6-for-13) in four games with the Nationals. He was acquired from the Yankees on July 31 in exchange for Minor League pitcher Jhonny Nunez.

The good news is that Gonzalez took batting and fielding practice on Thursday and didn't have any problems. He mostly likely will go to Florida and start a rehab assignment soon.

The Nationals had to make some changes to their lineup on Thursday. Shortstop Cristian Guzman and catcher Jesus Flores were late scratches because of left thumb soreness and a stomach virus, respectively.

Ryan Langerhans is still experiencing back tightness, but manager Manny Acta doesn't believe Langerhans will be placed on the disabled list.