Williams’s nerves so far are reminiscent of the last Grand Slam final she played against an unproven “next big thing”: Maria Sharapova in the 2004 Wimbledon final. Williams lost that match, 6-1, 6-4.

Osaka to serve for the set

When the two first played in Miami, Osaka said her first goal was to play well enough to make Williams shout “Come on.” She got that wish in the sixth game of this match, with Williams screaming one of her loudest after going up 15-30 on Osaka’s serve with a forehand winner.

Williams then earned her first break point of the match with a swinging forehand volley to go up 30-40, only for Osaka to save it with a 117 m.p.h. ace down the middle. Williams quickly gained a second break point when Osaka netted a backhand, and this time was able to send back a 116 m.p.h. serve. Osaka won the ensuing nine-shot rally.

Osaka converted her first game point with another 117 m.p.h. serve, this one out wide.

Serving at 1-5, Williams hit her fourth double fault of the match to go down by 0-30, but won four straight points to hold for 2-5, including three unreturned serves.

Osaka will now serve for the first set.

Osaka breaks Williams again

Osaka is off to a commanding lead, leading by a double break, 4-1. The DJ is playing Alicia Keys’s “This Girl is on Fire” during the changeover, appropriately.

Osaka, who is coached by Williams’s longtime hitting partner Sascha Bajin, has started the match with poise and tactical clarity. Osaka has been picking on Williams’s backhand to great effect, drawing five forced errors and four unforced errors off that side already, while holding Williams to zero winners.

Appearing the more nervous of the two, Williams has double-faulted three times.

Osaka takes an early lead

Serena Williams held to open the match, recovering from a 0-30 deficit. Osaka did the same and then broke Williams to take an early 2-1 lead.