Doc Rivers’ message was short and to the point.

Following the Celtics' Game 1 loss to the Lakers, he imparted a few words that would resonate throughout the series.

“He said, 'Rebounding is the key,' ” Kendrick Perkins said prior to Game 2. “Those were his last remarks — that rebounding was the key.”

The Celtics knew what would happen if they let Lakers big men Andrew Bynum and Pau Gasol dominate the glass.

It happened in Game 1, when the two combined for 20 boards and the Lakers outrebounded the Celtics, 42-31. Kevin Garnett looked stifled by Gasol — a new and improved version since the 2008 finals — and Bynum proved just how good the Lakers could be with him on the court.

The Celtics bounced back with a Game 2 win and a 44-39 advantage on the glass. But in Game 3, Bynum and Gasol grabbed 10 rebounds apiece as the Lakers won the rebounding battle and the game.

But fighting back didn’t take a groundbreaking master plan.

There are no plays drawn up for rebounding. It happens with effort, not the execution of X’s and O’s.

The Celtics have won the rebounding battle in their three victories this series, including Sunday's Game 5 in which they outrebounded the Lakers 35-34. While Gasol grabbed 12 boards, Bynum (who has been hampered by a knee injury) pulled down just one.

“It’s just effort. It’s all effort,” Perkins said after the game. “I thought we came out, put forth the extra effort, and we’re doing it as a whole, as a team. Everybody’s coming in and getting rebounds, big rebounds, at huge times, and that’s what we need.”

And with that effort, the Celtics, who looked helpless in the paint at the start of the series, are up 3-2 in the best-of-seven series against a Lakers team that has been quieted down low.

The C’s have owned the paint since being outscored there 48-30 in Game 1. They have a 56-point edge in the past four games, including a 46-32 advantage in Game 5.

Part of that is being aggressive in the lane. Another part is attacking the defensive glass and scoring on fast breaks at the opposite end. On Sunday they outscored the Lakers 14-3 on fast break points.

“They just played tough basketball tonight,” Lamar Odom said. “They got to the boards, especially on the defensive glass. We weren’t getting stops and they were getting a lot of rebounds — key rebounds — and we can’t let that happen.”

Without getting stops in the paint, the Lakers watched as Kobe Bryant’s spectacular third quarter was rendered relatively meaningless. Even though Bryant scored 19 points in 10 minutes, the Celtics still had a two-point edge in the quarter. They maintained the lead by attacking the basket. The C’s drew two fouls on Gasol as they outscored the Lakers 16-6 in the paint in the third.

“When [Kobe] did that, we didn’t take advantage of it,” Bynum said. “We allowed them to get easy baskets right back. All the work went for nothing. We can’t allow that to happen. We have to get stops and get rebounds.”

Both teams understand the impact that rebounding has had on this series. Even though the Celtics had the edge in Game 5, the Lakers are going back home where they are looking to dominate the paint on their own court. The C’s have to stay active while preventing the Lakers from doing the same.

“We’re hitting first,” Perkins said. “Our guards are coming in and getting long rebounds. Kev, Rasheed [Wallace], Baby [Glen Davis], myself, we’re pretty much doing a pretty good job on the inside. We could do a better job on the glass. We gave up 16 offensive rebounds today.”

As the Celtics study game tape and prepare for Game 6, the words imparted by their coach at the start of the series will echo loudly as they try to close it out.

“Doc said in order for us to win this series and win games, we’ve got to make sure we do it on the defensive end and rebounding,” Perkins said. “He said the team that rebounds the ball the best pretty much wins the game, so we’ve got to make sure we keep a great focus in doing that.”