Stanford’s No. 1-ranked and defending national-champion women’s soccer team opens the NCAA tournament against Seattle on Friday night at Cagan Stadium.

No. 5 Santa Clara and San Jose State also begin tournament play this weekend. The Broncos host Horizon League champion Milwaukee on Saturday afternoon. The Spartans face second-seed UCLA on Friday night in Los Angeles.

The Cardinal (17-0-2) won the Pac-12 title for the fourth straight year, going 10-0-1 in conference play. The only blemish in their league record was a 1-1 tie at Washington State on Oct. 28.

Stanford’s other tie came in a 1-1 tie in Santa Clara.

The Cardinal outscored their opponents 51-9 even though one of their best players, defender Tierna Davidson, played just three games because of her play with the U.S. national team and then an injury.

Sophomore Catarina Macario leads the team with 12 goals and five assists. Freshman Sophia Smith, third on the team in scoring with seven goals and 16 points, will miss the game because of an injury.

Seattle (10-7-3, 6-1-1 WAC) won its conference tournament to land the automatic berth.

NCAA women’s soccer tournament FIRST-ROUND MATCHES (With seeds in parentheses) San Jose State at UCLA (2), 6 p.m. Friday Seattle at Stanford (1), 7 p.m. Friday Milwaukee at Santa Clara (3), 1 p.m. Saturday

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If the Cardinal beat the Redhawks, the second- and third-round matches will be played at Cagan Stadium, Nov. 16-18, with the quarterfinal round, if necessary, scheduled Nov. 23. Stanford has reached the College Cup, the national semifinals, seven times in the past 10 years. The Cup will be played in Cary, N.C.

The Cardinal take a program-record 41-game unbeaten streak into the postseason. It’s the sixth-longest streak in NCAA history.

Santa Clara finished the regular season 16-3-1, with the most wins for the program since its 17-2 national-title season of 2001. The Broncos’ 9-1-1 nonconference record was their best since 2001, when they went 10-1. Milwaukee won the Horizon League’s automatic bid with a 16-1-1 record.

“It’s so hard to get one of the top 16 seeds out of 330 Division I teams, and we were able to do that,” Santa Clara head coach Jerry Smith said.

Besides tying Stanford, his team beat North Carolina 1-0. Both of those teams received No. 1 seeds. “We feel like we’re as prepared as we’ve been in our recent history for success in the tournament,” Smith said.

Redshirt senior Maria Sanchez is tied for the lead in the country with 14 assists, the most by a Bronco in 16 years. Junior Maddy Gonzalez leads the team with eight goals. Sophomore Kelsey Turnbow and redshirt junior Kelcie Hedge have each scored seven.

San Jose State will make only its third appearance in the tournament. No. 6 UCLA finished second in the Pac-12 behind No.1 overall seed Stanford with a 9-2-0 record and is 14-3-1 overall. The Bruins are on a nine-game win streak.

“Oh, we’re excited,” San Jose State head coach Lauren Hanson said. “Half of our team is from Southern California, so we should have a ton of fans there.”

The Spartans won the Mountain West Conference tournament and finished 9-6-6 overall. They had 11 shutouts, tied for fourth most in the nation.

Tom FitzGerald is a San Francisco Chronicle staff writer. Email: tfitzgerald@sfchronicle.com Twitter: @tomgfitzgerald