WASHINGTON -- Ryan Zimmerman got back to baseball work on Tuesday, but the Nationals still don't have a firm timetable for when he'll go on a rehab assignment -- or of his return.

Manager Jim Riggleman said that Zimmerman, placed on the disabled list on April 12 with a left abdominal strain, played some catch at a distance of about 60 feet Tuesday. He also did some tossing and running, all at approximately 50 percent effort.

Riggleman said that Zimmerman might try to do a little more of the same activities in the few days, basically putting in some more work as time goes on.

The skipper also said that he thinks the third baseman is going to do some kind of rehab assignment before coming back to the Nationals' lineup, but he can't pinpoint a time for that just yet.

"I would think he would [do rehab] eventually, but I have no idea when we might do that," Riggleman said.

Riggleman also said they want Zimmerman to be careful so he doesn't re-aggravate this injury, one that seems to have bothered several players in the Major Leagues already this year.

But he also said he's not worried about Zimmerman finding his stroke at the plate, since the third baseman seems to do that rather quickly.

"The one thing about Ryan is once he can do the other stuff, once he can take the ground balls and throw and run at full speed ... that he doesn't take long to find his swing," Riggleman said.

Desmond on paternity list; Bernadina called up

WASHINGTON -- The Nationals placed shortstop Ian Desmond on the paternity leave list on Tuesday and recalled outfielder Roger Bernadina from Triple-A Syracuse.

Desmond's wife, Chelsey, gave birth to their first son on Tuesday, Grayson Wesley Desmond, who came into the world in Sarasota at 3:56 p.m. at a weight of six pounds, 11 ounces.

The paternity leave period is three days, and Nationals manager Jim Riggleman said he thinks the shortstop will return Thursday.

"I think he'll miss tonight, likely tomorrow and be back the next day," Riggleman said.

Desmond has a .205 average with two home runs and eight RBIs in 20 games. Desmond's eight stolen bases have him tied for third in the National League.

Bernadina had a .267 average in 13 games with Syracuse and is tied for ninth in the International League with nine steals.

"I'll probably use [Bernadina] off the bench at this point," Riggleman said. "There's nothing set that he's the guy who goes back, either. He may stay and somebody else may go back."

Starters' five-inning streak extended to 22

WASHINGTON -- After Jordan Zimmermann's 5 1/3 innings against the Mets on Tuesday night, the Nationals remain the only team in the Majors who've had starting pitchers go at least five innings in every game this season.

Through 22 games, Washington's starters have shown the kind of consistency that makes life easier for the bullpen.

Nationals manager Jim Riggleman said things are a little easier for the starters this year because in 2010, some of them were somewhat restricted because of various health issues. But things are different this year.

"This year, there's no limit on anybody out there," Riggleman said. "It's just, 'Go pitch.'"

That also gives Riggleman a little more freedom, but the manager said the best part about the way the starters have fared is that they've kept the Nationals in the game on a regular basis.

"To this point, they've stayed in the game long enough to give us an opportunity to win a ballgame each night," Riggleman said.

Worth noting

The next pinch-hit for Matt Stairs will be the 100th of his career. When that happens, he'll be the 19th player to reach that plateau, and he'll tie Rusty Staub for 18th on the all-time list. ... Stairs also has 61 pinch-walks -- which are tops among active players. ... The Nationals are going to be busy in the coming days, as they'll have 16 games in the same number of days. They'll also have 32 in 33 days from April 23 to May 25. ... The Washington/Montreal franchise has 346 victories over the Mets. No other team has beaten them that many times. ... Jerry Hairston Jr. of the Nationals gets to compete against his brother Scott, who is with the Mets.