Ailing Perkins leaves early

The Celtics' Ray Allen can't find a passing lane surrounded by Derek Fisher (left) and Lamar Odom in the first quarter. (Barry Chin/Globe Staff)

LOS ANGELES - Center Kendrick Perkins was forced to leave last night's Game 4 victory with a left shoulder strain with 9:35 remaining in the third quarter, but he's hoping he'll be OK to play Sunday night.

Perkins came up clutching his shoulder after fouling the Lakers' Lamar Odom, his fourth foul of the game. After being hunched over by the Celtics bench, he went back to the locker room, grimacing in pain. Adding insult to injury, Odom made both free throws to spark a 7-0 Laker run that put the Celtics down, 67-48.

Perkins didn't return to the game, finishing with just 2 points and one rebound in 13 minutes.

"It's nothing but a shoulder strain," said Perkins. "It was too sore to go back in the game tonight. But on Sunday it will be fine.

"I think [Pau ] Gasol was holding my left arm. Any time you strain your shoulder it hurts. For the next three days I will rest and take care of my body."

Shot in the arm
With Rajon Rondo and Sam Cassell (wrist) ailing, the Celtics relied on Eddie House to give them a lift.

Never mind that the veteran guard had logged only 111 minutes through the team's first 23 playoff games, 20 of which came in Tuesday's Game 3.

"I consider myself playing in every game regardless when my number is called. I try to be ready," said House, who played 25 minutes last night. "I shoot the basketball. I'm not going to let them take me out of my game. They were open shots and my shots."

House, who scored 6 of his 11 points in the Celtics' big third-quarter run, knew the Lakers could be rattled.

"We knew if we get it under 10 we would put a little pressure on them," House said. "We played hard. We got stops when we needed to. We came down and executed and took the ball to the hole."

Unfavorable format
Game 5s have been key for the Celtics in the playoffs. They were tied, 2-2, in each of their three previous series, and all three times Boston won Game 5 at home. The switch to a 2-3-2 format for the Finals means they will have to win on the road Sunday to stay perfect in Game 5s.

"For us this postseason it's been crucial," said veteran big man P.J. Brown. "We've come back at home in Game 5 and that's almost like the Game 7 of the series because that game gives you so much momentum heading into the next two. It helps out at lot. It means a lot and Game 5 will be crucial in this series, too."

Brown said the Celtics simply have to block out the fact they're not at home this time.

"You got to somehow get your mind right and focused," he said. "If you're in a 2-2 situation or a 3-1 situation in the other format you were able to go home and get that home crowd behind you and you can get that game and get that energy, but unfortunately we're not in that position."

Celtics guard Ray Allen said that the 2-3-2 makes things more interesting, but he'd be in favor of an alternate format for the Finals. The NBA switched to 2-3-2 in 1985, when the Celtics and Lakers met for the second straight year.

"Just for the sake of the series and to keep people on edge, I'd like to see 2-2-1-1-1," said Allen. "It changes just like that so easily. It adds a little bit more drama."

Brown said he is in favor of the 2-2-1-1-1 format.

"I'd rather not be on the road this many days," said Brown. "I'm already ready to go back to Boston."

Rondo restricted
Rondo ended the suspense surrounding the bone bruise on the inside of his left ankle prior to Game 4, pronouncing himself good to go.

Rondo injured the ankle during the third quarter of the Celtics' 87-81 loss in Game 3.

Rondo clearly had some fun pregame with the fuss surrounding his ankle. When asked at what percentage he'd be at last night - he had said 50 percent on his blog after the injury happened and raised it to 70 percent prior to practice Wednesday - Rondo responded with 85 percent the first time. Then he upped it to 87.2 percent the second time he was asked, then 89.4 percent the third time, before finally sheepishly settling on 89.55 percent.

"It feels a lot better. I might get a tape job on it, but it feels better than [Wednesday]," said Rondo.

The second-year point guard was able to test his explosiveness Wednesday in practice by catching an alley-oop lob. He played just 18 minutes last night, coach Doc Rivers opting for House to run the offense in the second half.

Offensive comments
Rivers defended Kevin Garnett, who has come under fire for his lack of offense in the series. Entering Game 4, Garnett was averaging 18 points per game, but shooting just 35.5 percent from the field. He went 6 for 21 in Game 3.

Last night he was 7 of 14, contributing 16 points and 11 rebounds.

"I liken him a little bit to Patrick Ewing. Playing for the Knicks, I remember everyone complaining that Patrick Ewing took too many jump shots," said Rivers. "I used to laugh. Well, he made most them, so why shouldn't he take them?