"I don't know," said De La Rosa, who walked four, hit one and gave up a first-inning solo shot to Jorge Cantu. "I was so wild."
While winning his previous two starts, De La Rosa (5-6) gave up two runs in 12 1/3 innings. He's a threat to dominate each time out. On five occasions, he has struck out six or more.
But he's also perfectly capable of a mess like Thursday's, which left 13,634 at Dolphin Stadium delighted as the Marlins stayed 1 1/2 games behind the Phillies in the National League East. De La Rosa hasn't lasted five innings in any of his losses.
Despite the loss, the Rockies are 4-3 so far on a 10-game road trip that'll go a long way toward proving whether they still have hope of contending in the NL West. But the Rockies know that they don't have a lot of time to figure out De La Rosa.
"I don't know," Rockies manager Clint Hurdle said. "Write what you saw. That's kind of where we are with it."
The game was especially galling considering the happy feelings the Rockies carried into the contest.
Thursday afternoon's non-waiver Trade Deadline passed without the club making a move, even though there had been speculation the club would adopt a seller's stance and jettison closer Brian Fuentes and possibly others.
They weren't shaken by the Dodgers' acquisition of slugger Manny Ramirez. They were undaunted by the seven games by which they trailed the West-leading Diamondbacks or the six games they were behind the Dodgers. And De La Rosa had momentum.
"The last two outings I threw very good because I had very good command of my fastball and changeup," De La Rosa said.
But by the time De La Rosa had walked in two runs -- reliever Kip Wells would walk in another -- all the Rockies wanted was to get off their feet. Feeling some of his regulars had grown tired of watching ball after ball, Hurdle began removing starters in the middle of the game.
"Tonight was real tough," said shortstop Troy Tulowitzki, who stuck around for the whole game and went 0-for-5, ending his hit streak at six games. "You're standing out there what seems like three-fourths of the game.
"It's just tougher to take when you see how good he can be, a lefty throwing 94 [mph]. You see it's there. But sometimes he can't throw strikes. I'm sure he's battling through it and trying to fix things."
Wells absorbed four runs in 3 1/3 innings, including a solo shot by Hanley Ramirez.
The Rockies, on their heels because of their own poor pitching, were merely bit-part players in the comeback of Marlins righty Anibal Sanchez (1-0), who gave up two runs in 5 2/3 innings in his first start since undergoing right shoulder surgery on June 21, 2007.
The Rockies could turn their attention to their own little comeback story.
Left-hander Jeff Francis, who was stellar last season but subpar early this season because of left shoulder inflammation, dominated Thursday night in his third and most likely final injury rehab start at Double-A Tulsa. He struck out nine in six scoreless innings.
As long as there are no setbacks, he could return Tuesday night at home against the Nationals.
"I think we've got a spot for him," Hurdle said. "We need him back and productive."
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.