"Maybe I'll play," Castillo said.

Oliver Perez and John Maine threw batting practice at Citi Field before yesterday's 4-3 loss to the Marlins, continuing their atypical between-starts practice of facing hitters.

Manager Jerry Manuel said it was partly designed to remedy their early season struggles, and also to get acquainted with the Citi Field mound.

Reliever Casey Fossum declared for free agency rather than report to Triple-A Buffalo. He had been designated for assignment Sunday to clear room for Ken Takahashi.

The Mets indicated that the outbreak of swine flu in the New York area hasn't resulted in any changes at Citi Field yet.

"We, to date, have yet to receive any directive/direction from any government agency," a team official said.

Understandably, Oliver Perez is among the most concerned, since he has a sister living in Mexico City.

"Everything's okay," Perez said.

The first umpire video review in Citi Field history confirmed Fernando Tatis' sixth-inning solo homer. It was Tatis' first longball since Aug. 26 at Philadelphia, three weeks before he separated his right shoulder diving for a ball at Nationals Park.

Single-game tickets for June-October regular-season games go on sale Sunday at 10 a.m. at Mets.com and by calling (718) 507-TIXX. ...

Nelson Figueroa limited Rochester to one run in seven innings in his return to the organization, but Triple-A Buffalo lost, 1-0, to drop to 2-16. Nick Evans snapped an 0-for-21 skid, but is hitting .102. ...

Citi Field's spacious gaps are becoming a triples paradise. Jose Reyes and Jeremy Reed each had three-baggers yesterday, upping the team's MLB-leading total to 11.