Given the task of protecting a slim lead for the third straight game, Jonathan Papelbon was instead charged with his third blown save of the season in the bottom of the 10th inning.
It was more bad luck than bad pitching that allowed the Dodgers to rally from a 3-1 deficit, but that was little consolation for a team desperately trying to get back into contention.
In a hushed visiting clubhouse afterward, the often excitable Papelbon was among the most subdued Phillies as he stuffed his belongings into a red equipment bag.
"It was just one of those outings, there really isn't much you can do about it," Papelbon said. "I mean, for the most part, I felt like I made the pitches I wanted to make. Swinging bunts and bloop hits and infield hits and stuff like that, you can't really do much about them. It's just part of the game."
Like Papelbon's previous blown save in New York a few days before the all-star break, this one was deeply debilitating because it meant the Phillies had wasted a brilliant performance from lefthander Cliff Lee and a huge hit from Hunter Pence in the top of the 10th.
It also ended the Phillies' winning streak at four games and cost the team a chance to finish off a three-game sweep for the first time this season.
The team went 4-2 on the six-game road trip to start the second half, but it cannot afford to let games like this one slip away, because the Phils are trying to dig out from an avalanche of first-half losses.
"It was a tough loss," manager Charlie Manuel said. "It was a real tough loss. We won two series, but at the same time we go home 4-2 instead of 5-1. The one game, that's big right now for us."
Pence's two-run chop single off Javy Guerra in the top of the 10th had given the Phillies a two-run lead. Papelbon's turbulent bottom of the 10th started with Luis Cruz's leadoff double and continued when pinch-hitter Bobby Abreu dropped a bloop RBI single into shallow left field with one out.
After Abreu stole second base, Tony Gwynn Jr. reached on a swinging bunt single in front of the pitcher's mound. Papelbon struck out Mark Ellis to get within an out of ending the game, but Kemp got the tying run home with an infield single when he just beat a throw from deep shortstop by Jimmy Rollins.
Papelbon kept the game tied by retiring Andre Ethier, but that just prolonged the agony until the 12th, when Diekman left a fastball over the middle of the plate and Kemp crushed it into the right-center-field seats.
"We've got to look at the bigger picture and realize we came on the road and took two series," Papelbon said. "That's the kind of start we need [after the break]. Should we have swept these guys? Yeah, sure, but we have to stay positive and look at the big picture and know that we came out after the all-star break and did our job in these two series."
After a mighty struggle to come through with runners in scoring position through the first half of the season, Pence was Mr. Clutch during the road trip. He hit his first three-run home run of the season Sunday in Colorado to ignite a victory, then delivered a game-winning single Tuesday night before coming through with a big hit again Wednesday.
Other than Pence's two-run single in the 10th and an RBI single from Carlos Ruiz, the Phillies did not have much offense in the series finale. That was unfortunate for Cliff Lee, who surrendered just one run and two hits in eight innings.
Dodgers lefty Clayton Kershaw also allowed just one run in eight innings. The Phillies finished the game 2 for 10 with runners in scoring position.
Contact staff writer Bob Brookover at firstname.lastname@example.org or on Twitter @brookob