The Nationals will place third-string catcher Carlos Maldonado on the disabled list with a lower back strain and recall outfielder Tyler Moore from Class AAA Syracuse, Manager Davey Johnson said.

Moore could have a short stay with the Nationals. Johnson indicated earlier today that the Nationals will likely use an eight-man bullpen once Brad Lidge returns over the weekend. Moore would be the likeliest candidate to be moved off the 25-man roster.

In his first stint in the majors, Moore, 25, went 3 for 19 in very limited action. Maldonado becomes the 13th player — and third catcher — to land on the disabled list this year for the Nationals.

Tonight, Lidge retired all three hitters he faced while pitching one inning for Potomac, striking out two.

In other news, utility man Mark DeRosa, who has been on the disabled list for six weeks with a strained oblique, will begin a rehab assignment either Thursday or Friday at Class A Potomac.