Rzepczynski available to pitch tonight, Lopez optioned to Triple-A

Marc Rzepczynski has arrived in Washington. And apparently traffic was light enough getting into town from Dulles that the newly acquired reliever has made it to Nationals Park in time to be eligible for tonight's game.

"There's a chance," manager Dusty Baker said earlier this afternoon, perhaps underestimating how difficult it typically is to make that 30-mile drive into town during rush hour.

Turns out Baker's optimism was warranted, though, and so Rzepczynski will be at his disposal out of the bullpen tonight against the Orioles should they need him.

To make room for the left-hander on the active roster, the Nationals optioned Reynaldo Lopez to Triple-A Syracuse, giving the club eight relievers and only four starters for now.

In acquiring Rzepczynski from the Athletics for minor league infielder Max Schrock, the Nationals believe they've addressed their most pressing current need: An experienced left-handed reliever who can be counted on to be available back-to-back days for the stretch run.

Rzepczynski has pitched in an average of 65 games each of the last five seasons and is on pace to make 72 appearances this year. With rookie Sammy Solis on the disabled list with shoulder inflammation and Oliver Perez in a prolonged slump, the Nationals desperately needed a reliable lefty reliever.

"I think it was a necessary move because we've only got one left-hander," Baker said. "And especially with Solis down, we were hoping we'd get some reinforcements, especially on the left side. His stats and his track record look very good. I think he can help us."

Rzepczynski's numbers this season (3.00 ERA, 1.722 WHIP, lefties hitting .296 vs. him) don't blow anyone away. But his reputation for getting ground balls - he has one of the best rates in baseball - and recent success with the Athletics made him attractive to the Nationals.

"It's always a plus when you can induce ground balls because you get a chance to turn double plays, you get a chance to get out of trouble," Baker said. "So we've got one that's one of the best at inducing groundballs in (right-hander Blake) Treinen, and now we've got one from the left side. We can always use those guys to induce ground balls. It's a welcome sight and a welcome addition. And when Sammy gets back, we'll have three of them."

The decision to demote Lopez back to the minors will have a domino effect on the Nationals rotation. The rookie right-hander, who was roughed up Tuesday night at Camden Yards, was slated to start Sunday against the Rockies. Now the club will need to promote another starter - most likely Lucas Giolito - for that game, which means they'll need to drop another player at that point.

The Nationals did not, however, need to clear a spot on the 40-man roster for Rzepczynski because they already were at 39 after releasing Jonathan Papelbon.