PHILADELPHIA – There were three numbers that jumped out at Celtics coach Doc Rivers as he tried to explain his team’s exasperating loss in Game 4 of the Eastern Conference semifinals. They were 17, 17 and 36 as in: offensive rebounds, turnovers and free throws. It was the last number that bothered the coach so much.

“The free throw line tells the story,” Rivers said. “Thirty six attempts to nineteen. That’s tough to win that way. Everything we did was the prescription that you don’t do to beat them. You would have thought that we were down the whole game if you looked at those numbers, yet we had the lead.”

The free throw line did tell the story. The Sixers were far more aggressive going to the basket, while the Celtics could never establish an inside game. Kevin Garnett took only 12 shots and just three were inside the paint. He also had seven turnovers.

“We took it away from ourselves,” Rivers said of the non-existent inside game. “They took it away too, but we had a lot to do with it. We took it away. We did more than settle [for jump shots]. We just lost our composure.” 

Here’s the other telling part of the Celtics’ 92-83 loss. Those numbers were just as bad – if not worse -- in the first half when they were building a 15-point halftime lead. They allowed 10 offensive boards in the two quarters and turned it over nine times. The free throws were 21-5 in Philadelphia’s favor at the intermission.

But something changed in the second half and it started in the first few minutes when the whistle-happy crew of Scott Foster, Bill Spooner and Bill Kennedy called seven fouls –and two technicals in the first three minutes and five seconds. After Elton Brand picked up a retaliatory technical against Kevin Garnett, Philly went on a 10-0 run. What had been a clean and efficient clinic on how to deliver the knockout punch on the road, turned into a desperate game of survival.

“When you have a chance to go up 3-1 in a series and you’re up, what else are they going to do? That’s what they should do. That’s what so disappointing,” Rivers said. “They’re going to get into you, they’re going to grab your hand, they’re going to foul you. To me that’s what they should do, but we acted like we were surprised by it and so I was disappointed in that.”

The Celtics didn’t make their first field goal of the half until the 5:04 mark when Paul Pierce hit a 3-pointer, and they shot 11-for-35 in the second half. Philly thrived in the suddenly charged environment, shooting over 50 percent and committing just four turnovers, while outscoring the Celtics, 61-37.

“Once they picked up their intensity I don’t think we played with a sense of urgency in the third and fourth,” Pierce said. “That’s a chance when you have a team on its back. You’re up 15 and you can take their confidence and we didn’t do that. That was really on us.” 

The trouble started when Avery Bradley picked up his fourth at the 9:20 mark. The Celtics were up by 17 points when Bradley went out. By the time he came back in the fourth quarter, they were down by one. Bradley had been doing a marvelous job on Evan Turner and the Celtics clearly missed his athleticism and speed as the game began to change from Boston’s methodical pace to Philadelphia’s helter-skelter style.

Brandon Bass – who played his best game of the playoffs with 15 points and five rebounds – also joined Bradley on the bench after he picked up his fourth foul at the 7:21 mark. Bass didn’t get back on the court until there were three seconds left. Rivers rode his small lineup that had been so effective in this series, but was at a loss to deal with the likes of Thaddeus Young, who had eight points and seven rebounds in the second half.

“Regardless [of the foul trouble] that shouldn’t have affected how we played,” Rajon Rondo said. “We’ve got 15 guys on this roster and our bench players have played great this series. We’re not a team that points the finger. We just went in a lull and couldn’t score the basketball at that particular time.” 

While the Celtics couldn’t recapture their rhythm offensively, the Sixers repeatedly broke down their defense. Lou Williams and Andre Iguodala combined to make 10 of their 15 shots, while Young and Lavoy Allen beat them for loose balls and hustle plays. The Sixers reeled off 11 of the final 13 points in the last three minutes and turned into a two-point deficit into a nine-point win.

“They made some shots,” Rondo said. “Give them credit. They made a lot of big shots down the stretch. They outworked us a couple of possessions. They played hard. They kept fighting.”

The Sixers have breathed new life into a series that was staring at its expiration date in Monday’s Game 5 back in Boston. Shaking this Philadelphia team won’t be easy.

“No matter what people say, it’s not over until it’s over,” Iguodala said. “Being down 3-1 is a total different mentality than being at 2-2.  It could swing either way.”

It really could. The Celtics felt like they had to steal a game on their homecourt just to go to Philadelphia with a split. Now they have to hold serve to come back here with the advantage. The Celtics have played one and a half good games in this series and in many ways they’re fortunate to still have homecourt advantage.

“On the road you got to really put the knockout punch to the teams when you have them down,” Pierce said. “And we just didn’t do that.”