The general consensus is that Rajon Rondo is one of the major keys to this series. Therefore the big question on everyone's mind is "who will guard Rondo?" I suppose it makes a difference in the half court, but to me the more important question for L.A. is "who is going to catch up with Rondo?"
You see, the Celtics have shown us something through the first 3 rounds. Despite the constant stream of jokes about their age (even from Doc!), this team can run the break. This isn't the Suns or the Showtime Lakers of the 80's, but it is actually a lot like the Celtics teams from the 80's. People forget that those teams ran the ball very well. It was opportunistic fast breaks ignited by turnovers and rebounding and it worked beautifully because there was a commitment to it. This team is showing a lot of that same knack for the break, and those 80's teams never had anyone as dynamic as Rondo to lead the break.
But don't just take my word for it. Here are some other opinions:
Their spotty half-court offense doesn't matter as much because they don't need it as much. Throw in Rajon Rondo, the league's best point guard (outside of maybe Deron Williams) at pushing the ball up the court, and you have a recipe for success. Even if Rondo doesn't create a fast break, he's so good at finding a mismatch to exploit before the other team's defense gets set. That's how the Celtics have been winning in the playoffs, and if they're to win this series, that's how they'll have to do it.
With Kobe Bryant likely checking him, Rondo will have ample time to scope out cross-match advantages after a long rebound or Laker turnover. Bryant can use his length and smarts to lock Rondo down when the game slows to a crawl, but in the haze of moving screens and switched assignments, Rondo should have an advantage in transition. And if Ray Allen should deign to join him, say run to a corner or elbow extended, then the Celtics could really find an advantage, here.
More praise of Rondo, from the Godfather of Point Guards himself, Bob Cousy.