Serena Williams faced her first big test since she unexpectedly lost in the Australian Open final to Angelique Kerber 6½ weeks ago. Williams' response Tuesday night was an imperious statement aimed at her most dangerous rivals. Williams, the top seed at Indian Wells, overwhelmed defending champ and No. 5 seed  Halep, 6-4, 6-3, in a bruising display of power tennis. Here are five takeaways from the match:

1. Williams' serve sets the tone: Williams once again demonstrated the serve is the most critical shot in tennis. That doesn't just mean it's a shot capable of earning any number of points, it's also the foundation of her game, setting her up for everything that comes after. For someone like Halep, that will always be a challenge, because Halep's serve simply isn't good enough to guarantee her control of the point. Williams, by contrast, knows that if she serves well, she will get a bushel of free points (aces and unreturnables), plus the opportunity to dictate. Williams won 82 percent of her first-serve points in this match to Halep's 58. Williams out-aced Halep 7-1, and she forced three times as many break points with her return (9-3).

2. Halep needs another level: Halep might not be as ready as some think to take that next, big step to Grand Slam winner. The 5-foot-6 Romanian receives support on all fronts, from commentators to coaches to iconic players to fans. "It's not like a magic thing," Halep told reporters, describing her meeting with the famous tennis couple. "But mentally [the meeting and talk] was helping me a lot, because I changed a little bit my mentality, how to see the things now when I'm going to defend a title."

3. Serena's slow starts: Williams must find a way to get into matches more quickly more often. One of the problems that has made life more complicated for the 21-time Grand Slam singles champion recently is sluggishness. Against Halep, Williams once again had trouble dialing in her game. She made four straight unforced errors to give up a break and fall behind 1-2, but this time she quickly snapped to life. She broke, built a 5-2 lead and never trailed the rest of the way. It was tight and bright.

4. Bright lights too bright: Halep's shortcomings are most evident at big moments, which is part of what keeps her linked with the rank and file rather than the champions. Halep popped 80 mph serves right into Williams's wheelhouse on some important points. That just doesn't work against a player of Williams' caliber.

5. Don't forget the footwork: The key to Williams' game, once the ball is in play, is her footwork. When she goes through a patch when she's making too many errors, it's almost because she isn't moving her feet well. She tends to run through the ball when taking it while moving forward. Or she plucks a drive volley out of the air without making some small, albeit necessary, adjustment with her feet. This is a tricky issue, because the surest way to have good  ovement is to feel great enthusiasm. But sometimes it must be hard for a 34-year-old champion who has seen and done it all to feel that eagerness.