"For me, I was just catching too much of the plate today and wasn't as sharp as I have been here for most of the year," Papelbon said. "It was just one of those days I didn't have much on the baseball today, much control."
Papelbon, who entered the game having allowed just three earned runs in 27 career innings against the Marlins, had pitched the previous two nights against Miami.
"He's done that before and he's the closer," Phillies manager Ryne Sandberg said. "That's what they do, come in with a chance to close three games in a row. That's what a closer does."
"I mean, it is three in a row, it is what it is. I felt fine," Papelbon said. "I have done that situation plenty of times before and been fine and [it] doesn't really affect me, no."
The Phillies put the first two men on in the bottom of the ninth, but Ben Revere, Maikel Franco and Chase Utley struck out in consecutive at-bats to end the game.
The loss was just their fifth this season when leading after eight innings (54-5). The Phillies' bullpen entered the game with a Major League-best 1.92 ERA since Aug. 5, holding opposing hitters to a .200 average over that span.
"I don't remember the last one we lost in the ninth," Sandberg said. "We've been pretty solid winning after the seventh, eighth and ninth innings. I don't think it typifies us at all. I think our late-inning bullpen guys have been solid and when we've had a lead late in the game, we've been able to hold it. Played a good series. Obviously had a chance to sweep the Marlins, but we came up short and took two out of three."
Still, Buchanan's effort was a positive one for Philadelphia. On June 24, the 25-year-old went five innings and allowed two runs en route to a victory over Miami. But three months is a lifetime for a developing rookie, and Buchanan looked even sharper in his second go-around against the Marlins.
Buchanan went 6 1/3 innings and allowed one run on five hits and a walk while striking out two. His only blemish came in the top of the fourth, when Enrique Hernandez hit a solo shot that tied it at 1.
The Phillies scored their first run on an RBI single by Franco, who was making his eighth big league start.
In the bottom of the fourth, the Phillies scored two more, driving home a run on a double-play groundout by Domonic Brown and tacking on another on a single by Carlos Ruiz.
Buchanan's recent performances, as well as his continued growth, have made him a compelling option for the Phillies' '15 rotation. Since being recalled on Aug. 6, Buchanan has a 2.91 ERA (15 earned runs in 46 1/3 innings) in eight starts.
"I think me and Chooch [Ruiz] had a good one today and we worked well together," Buchanan said. "It's all a work in progress. You continue to improve every outing. As long as I stay true to myself, that's when I continue to progress in my game and get better at pitching in the big leagues."