LOS ANGELES — When it comes to the playoffs, adjustments are the name of the game. And for the Lakers and Celtics, the tactical changes they make to respond to the other team’s moves are going to be a big factor in determining who wins tonight’s Game 4 at Staples Center.

Los Angeles survived Game 3, 87-81, to cut the Celtics’ lead to 2-1, and a couple of key adjustments by Lakers coach Phil Jackson were major factors.

For starters, he switched up his defensive assignments by putting Kobe Bryant on Boston’s Rajon Rondo and Derek Fisher on the Celtics’ Ray Allen. This didn’t help the defense on Allen any, as he got loose for 25 points. But Bryant was better able to contain the penetration of Rondo, who dribbled through the Laker D to hand out 16 assists in Game 2.

Additionally, Bryant played a role in keeping Kevin Garnett and Paul Pierce under wraps. By nature, he’s a roamer at the defensive end, and his wandering tendencies were useful as a double-teamer anytime Garnett or Pierce got the ball down low. The Lakers dared Rondo to beat them with jumpers from the weak side, and by and large he couldn’t.

Of equal importance was the offensive improvement begat by the switch. Because Bryant and Rondo were paired up, if the Lakers pushed the ball quickly up the court, Rondo would inevitably have to cover Bryant at the other end. That created a size mismatch that the Lakers exploited several times in the first half, which is a big reason Bryant got to the free throw line so much more than he had in the first two games.

A second adjustment by Jackson later in the game also helped. With Rondo out of the lineup due to a sprained ankle, he switched Kobe onto Paul Pierce down the stretch. Bryant did an excellent job here too, helping limit Pierce to six points on 2-of-14 shooting.

So as we head into Game 4, it will once again be a battle of adjustments. And now it’s Doc Rivers’s turn to make them.

For starters, he faces an interesting dilemma at point guard. Rondo’s ankle sprain is a much more serious problem than the one suffered by lumbering center Kendrick Perkins in Game 1, because, as a small, quick guy, Rondo has to be at top speed to be effective.

That could force him to turn to the likes of Eddie House and Sam Cassell, whom he’s alternated using as his backup point guards during the postseason. House played the bulk of the second half in Game 3, as the Celtics tried to neutralize the double-teaming of Garnett in the post by putting the sweet-shooting House on the weak side.

However, House struggles bringing the ball up against pressure, and he isn’t nearly the passer or defender that Rondo is. Cassell, meanwhile, is a veteran gunner who has been a little too brazen about looking for his offense during the playoffs. But his hot stretches — such as the second quarter of Game 1 — have enabled Boston to get offense while Garnett and Pierce rest.

If Rondo can’t go, there’s also a possibility Rivers will get creative. At yesterday’s press conference, he alluded to the possibility of playing — even starting — little-used Tony Allen at the point. He also has the option of using Ray Allen as his point guard and going with a big lineup that has Pierce and James Posey on the wings. Either of those alignments would allow Allen to guard Derek Fisher instead of Bryant and put a better one-on-one defender on Kobe.

Meanwhile, Rivers also should consider an adjustment up front. Thus far in the playoffs he’s been extremely reluctant to play bench ace Leon Powe and Garnett at the same time, preferring to use Powe solely as Garnett’s backup. It might be time to shift that around.

Powe was brilliant in Game 2, with 21 points in 14 minutes, and although he didn’t perform as well in Game 3, neither did primary frontcourt sub P.J. Brown. Powe was a vastly more effective player than Brown during the regular season, and the Lakers appear to have great trouble matching up against his physicality — even when he’s guarding much quicker players like Lamar Odom or Luke Walton.

From the Lakers’ perspective, Jackson can’t just sit back and assume everything’s fine now. They’re still trailing 2-1 and facing a must-win Game 4, and they have to feel fortunate that they escaped with a W in Game 3 after only two players scored in double figures.

One of them is Sasha Vujacic, whom Jackson ought to promote to the starting five. He pumped in 20 points in 27 minutes in Game 3, including a crucial 3-pionter with 1:53 left that gave L.A. an 81-76 lead, and for the series he’s their second-leading per-minute scorer after Bryant.

However, L.A. is wasting big chunks of the game with him on the bench and instead starting 6-foot-10-inch space cadet Vladimir Radmanovic at small forward, with disastrous results. He’s been ineffective offensively and abused by Pierce on defense, getting into quick foul trouble in both Games 2 and 3.

If Rondo is out for Boston, Jackson might try one other gambit — getting more minutes for backup point guard Jordan Farmar. He is far better at pressuring the ball than starter Derek Fisher, and he is also the more aggressive offensive player of the two.

That isn’t necessarily a good thing when he’s going against Rondo, who is a superior defender, but both House and Cassell are eminently flammable. In addition, those two struggle to bring the ball up against pressure, eating up valuable shot clock seconds. Farmar played 20 minutes in Game 3, including much of the second half, and could take on an even bigger role if Fisher — having a miserable series thus far — once again struggles.

The decisions Rivers and Jackson make on these questions may be the determining factor in Game 4, but as the tension builds heading into tonight, I’d like to suggest one final adjustment — by the Laker crowd. I was at Game 3 and all I can say is good heavens that was lame. Coming on the heels of the raucous crowds in Boston, it was shocking how little noise the L.A. fans made.

C’mon guys, it’s Lakers and Celtics in the NBA Finals! Everyone else is excited about it — can’t you be?

jhollinger@nysun.com