The Nationals also purchased the contract of catcher Pedro Severino from Double-A Harrisburg and recalled left-hander Sammy Solis from Triple-A Syracuse before Tuesday night's game at St. Louis.
The 35-year-old Uggla missed 22 games with back spasms and played seven games on a rehab assignment, batting .217 (5 for 23) with a homer and six RBI.
Uggla is batting .191 with a homer and 14 RBI this season.
Manager Matt Williams said outfielder Denard Span came out well from season-ending shoulder surgery to repair a small tear in the labrum. Williams says there was also some shaving of the bone to clear space, but added Span would begin therapy soon.
"He came through it well, the procedure went well, he's on the way to recovery," Williams said.
Pitcher Stephen Strasburg played catch and could be scheduled for a bullpen session if he feels fine Wednesday. Strasburg left Sunday's game against the Miami Marlins after four innings with upper back tightness and said after that game that he intended to make his next start.
Tanner Roark's start was abbreviated to two innings at Double-A Harrisburg on Monday so he would be available to replace Strasburg if necessary on Friday, against Atlanta.
Williams said right-hander Aaron Barrett, on the 60-day DL, will undergo elbow surgery.
The Nationals transferred right-hander David Carpenter, who has right shoulder inflammation, to the 60-day disabled list. Carpenter has not responded to therapy.
The 22-year-old Severino was hitting .249 with five homers and 34 RBI in the minors. This is the fourth call-up for Solis, who was 1-1 with a 5.54 ERA in 10 games.