Ryan Zimmerman performed some light throwing and running today, and although the plan is for the injured third baseman to increase incrementally his baseball activities over the next couple of days, Manager Jim Riggleman said there remains no definitive timetable for his return.

Zimmerman was eligible to return from the disabled list today following an abdominal muscle strain suffered on April 9 while sliding into second base. The original forecast was for Zimmerman to miss roughly three weeks, with the Nationals taking extra precautions to ensure he would not aggravate the injury by coming back too quickly.

Riggleman also said Zimmerman probably would go through a rehab assignment during dates to be determined before rejoining the Nationals, who open a seven-game home stand tonight starting with a three-game set against the New York Mets.

“The one thing about Ryan is once he can do the other stuff, once he can take the groundballs and throw and run at full speed, he doesn’t take long to find his swing,” Riggleman said. “You notice in spring training when he sat out, he got back in there within a day or two, and he was pretty much back on the ball. I think he’ll find timing at the plate relatively quick.”

The Nationals sure could use Zimmerman’s robust bat in the lineup. The former all-star was hitting .357 with a .536 slugging percentage and an OPS of 1.02. Washington is second to last in the big leagues in team batting average (.223) and fourth to last in slugging (.340).

During their most recent six-game road trip that concluded with last night’s 4-2 loss to Pittsburgh, the Nationals scored more than three runs twice, both victories. In the four losses, they managed just seven runs combined.

Zimmerman hurt himself when he slid into second base, taking an extra base on a single when the outfielder’s throw went to third. It was an especially unfortunate injury considering the ball never went to second base, thus not requring a slide. Zimmerman remained in the game and went 1 for 3 with a single.

Zimmerman missed significant playing time because of injury for the third time in four years. Although he did not go to the disabled list last year, he played 142 games, missing time at the end of the season with an oblique injury and also sitting out a handful of games early in the year with separate hamstring strains.

Zimmerman played 108 games in 2008 after he hurt his left shoulder, also when sliding headfirst. In 2007 he played in all 162 games, and he played 157 games in both 2006 and 2009.

“We want to make sure that he doesn’t reaggravate this injury because it just seems like it’s an area that throughout baseball a lot of players are dealing with today and missing significant time,” Riggleman said. “So we want to keep the days as short as possible on this end so it doesn’t extend later to be a real period of time that he would have to sit because he’s re-aggravated it.”