The No.1-seeded Williams looked rusty in her first two matches of the fortnight, but on Monday looked fantastic during a 63 61 win over American qualifier CoCo Vandeweghe - and she looked even better in this one, blasting 27 winners to just 17 unforced errors to defeat the No.5-seeded Kerber.
"I felt much better today than in a few of my other matches here," Williams said. "Knowing I was going to play a Top 10 player, I knew I had to come out and play really well tonight. And I did play well."
But the 17-time Grand Slam champion and World No.1 had more to add about her form.
"As the tournament progresses, you can't get worse, you have to get better," she said. "The good news is I can play better, so that keeps me really happy, knowing I can still play several levels higher."
Williams was already the most accomplished player in Sony Open Tennis history coming into this year's event with six titles and 61 match wins (Steffi Graf was the previous record-holder in both categories with five titles and 59 match wins). After four matches now, Williams has 65 match wins.
Williams leads Sharapova in their head-to-head series, 15-2, and has won their last 14 in a row.
"When you're playing champions, you have to play your best," Williams said. "She plays her best and her heart out against me - we just have to bring the best because we're both really good players."
But what about winning 14 matches in a row against Sharapova, a fellow Career Grand Slam holder?
"Well, I love playing her, I really do - doesn't matter what surface or anything," Williams said. "She's one of my favorite people to play. And so I think that helps when you're playing against people.
"It just gets you really pumped."