The trades of Josh Beckett and Dontrelle Willis and A.J. Burnett's departure via free agency have left Florida (43-40) without an ace. That wouldn't be much of an issue if the Marlins were languishing in last place, but they enter play Wednesday just 1 1/2 games behind NL East-leading Philadelphia.

Nolasco (8-4, 4.05 ERA) didn't seem like a candidate to be the staff ace after a right elbow injury limited him to five appearances last season. The third-year right-hander, though, is 7-1 in his last 10 starts, and has been particularly good in four starts since losing to Atlanta on June 5. He is 3-0 with a 1.82 ERA in that span while walking four and striking out 27.

Nolasco fanned nine over eight innings, allowing one run and six hits Friday in a 3-1 victory over Arizona. He is 3-0 with a 0.86 ERA in his last three starts at home.

"I know that he has gotten better every start, and he has been pretty consistent," Marlins manager Fredi Gonzalez told the team's official Web site. "This is what our people saw in '06. We didn't see it in '07 because of the injuries and that kind of stuff. But this is good. And he builds on every start."

He pitched six strong innings in a 7-3 win at Washington on May 9, improving to 3-1 with a 3.95 ERA five career starts against the Nationals.

Nolasco will try to help Florida win its second straight series and improve to 10-2 this season against Washington (34-51).

The Nationals earned a rare victory in the season series, winning 9-6 on Tuesday as Ronnie Belliard hit a grand slam to back a strong performance by Collin Balester, who allowed one run in five innings to win his major league debut.

Washington has won four of six after losing eight of its previous nine games.

Hanley Ramirez homered - his third in three days - and drove in a career-high five runs for Florida.

"It didn't matter, we lost the game," Ramirez said. "We've got to come back tomorrow and win the series."

The Marlins were without slugging second baseman Dan Uggla for a third straight game. Uggla, tied for the NL lead with 23 homers, is hoping to return sometime during the team's four-game series at Colorado, which begins Thursday.

Odalis Perez (2-5, 3.87) makes his second start for Washington since coming off the disabled list. The veteran left-hander tossed four scoreless innings Friday in a 4-2 win over Baltimore, but left after throwing 75 pitches because he missed the three previous weeks with shoulder tendinitis.

Perez has allowed three earned runs or fewer in four consecutive starts with the Nationals winning three of those games.

He has pitched well in two starts this season against the Marlins, limiting them to two earned runs in 11 2-3 innings while walking three and striking out 13.