Injuries are proving to be Houston's toughest opponent this season.
Houston has used the disabled list 16 times this season. If Everett goes on the DL, he will join seven other Astros currently on the list.
Everett, who is batting .331, hurt himself while making a throw to third base.
"These injuries are pretty unbelievable," said Astros slugger Jeff Bagwell. "I don't know what's wrong with this club. When Carl got hurt everybody just put their head in the sky and said, 'Oh, no!"'
The Astros left 12 men on base and managed just one run out of two bases-loaded, no-out situations.
"We had a lot of chances, we just couldn't get the key hits," Dierker said.
The Astros remained a half-game ahead of second-place Cincinnati in the NL Central. The Reds lost 8-6 to Montreal earlier.
A.J. Burnett (2-0) won his second major league start, allowing two runs one earned on four hits in five innings. He walked six and struck out five. Burnett, 22, beat Los Angeles 6-1 in his big league debut Aug. 17.
Florida manager John Boles was impressed with Burnett.
"He's good, he's got the stuff to go a long way," Boles said. "He's an unpolished stone; we need to chip away and polish and smooth away the edges."
"It shows that I have what it takes," Burnett said. "I'm not going to crash, never have and never will. I've handled pressure before and I'm going to give it all I've got."
Armando Almanza relieved with the bases loaded and none out in the seventh and escaped the jam. He struck out pinch-hitter Russ Johnson before getting Ken Caminiti on a popout and Matt Mieske on a fly to left to preserve a 4-2 lead.
Antonio Alfonseca pitched the ninth for his 13th save.
Scott Elarton (7-4) went six innings, giving up four runs one earned and seven hits for Houston.
After a walk to Bruce Aven, Castillo scored when first baseman Jeff Bagwell misplayed Kevin Millar's slow grounder for an error. Preston Wilson walked to load the bases and Lowell drove in Aven and Millar with a single up the middle.
The Marlins increased their lead to 4-1 in the fifth when Castillo, who went 4-for-4 to extend his hitting streak to a career-high 17 games, led off with a single and later scored on Aven's sacrifice fly.
"It's very important to set goals and I'm not surprised. This is the way I want to finish the season," Castillo said.
Houston cut it to 4-2 in the fifth when Biggio scored on Ward's groundout.
Castillo scored on Jay Powell's wild pitch in the ninth to make it 5-2.
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