Corona del Mar High's Karsten Sigband, left, goes up for a header against Northwood's Maren Martinez during a Pacific Coast League game at Northwood High on Thursday. (SCOTT SMELTZER, Daily Pilot / January 10, 2013)

IRVINE — The Corona del Mar High girls' soccer team had to take the bad with the good Thursday afternoon in its Pacific Coast League opener.

It was sunny at Northwood High, but it was also quite cold and windy at times.

And, though the Sea Kings opened league with a 2-0 victory over the Timberwolves, they also lost arguably one of their most important players.

Sophomore Brianna Westrup, the CdM center back, exited with a potentially serious right knee injury in the second half. The way the injury happened made the Sea Kings angry.

Westrup had been on the ground plenty throughout the game. Much of the time she was tangled up with Northwood junior Philine Qian. Westrup had earned a yellow card early in the first half. She complained when she ended up on the ground, but Qian earned the free kick.

The play in the second half was more egregious. Westrup had gained control of the ball and was ready to advance it up the field, before Qian appeared to kick her in the back of the knee. Westrup immediately fell to the ground in obvious pain, and was eventually carted off with a knee brace. Qian earned a red card and was ejected.

"For [Westrup] to be in that much pain, it probably will be something pretty serious," CdM Coach Bryan Middleton said. "She's a very tough individual."

Middleton told his players they needed to slap hands with Northwood after the game, even if they didn't necessarily want to do so. But Northwood assistant coach Tom Lancaster said he didn't think his player meant any harm on the play.

"It was a forward's challenge, chasing after she lost the ball," Lancaster said. "I don't think there was any malice there. I think she was trying to get the ball, and it was a poorly timed challenge in the end ... I first thought it would be a yellow card, but obviously the ref gave a straight red. The main thing is that [Westrup] is all right."

CdM already came into the game short-handed, still missing senior captain Annie Alvarado (groin) and junior Molly Keasey (Achilles). Freshman goalkeeper Kat Hess is in Las Vegas at the Region IV Olympic Development Program championships.

Middleton said all three players should be back next week for CdM, the two-time defending outright league champion. The Sea Kings (9-2-2, 1-0 in league), ranked No. 3 in CIF Southern Section Division 1, found the going tough early in Thursday's match.

They were going toward the north goal, against the wind. That made stringing together possessions against the Timberwolves (3-6-1, 0-2) difficult.

"We were going against the elements, against the wind," Middleton said. "I was hoping we'd open up a little bit more, but it's a crisp, cold day. The wind was affecting the game, and the small field does not play to our game."

Corona del Mar still struck first right at the end of the half, after a strong run up the right side from senior defender and team captain Alana Hunter earned a free kick. Another captain, senior midfielder Karsten Sigband, took the kick from near the CdM sideline. The Northwood goalie was unable to handle the ball in the box and Sigband's younger sister, sophomore Birkley, stuck it in.

"The goalie was pretty tall, so I wasn't really shooting it," Karsten Sigband said. "I was playing a hard chip, and hoping that it would just kind of bobble around. I figured that one of us would be able to put it in once it was in the mix, and luckily my sister got there and put it in for us. It's always fun when we can have those assists and goals together."

Middleton said it reminded him of last year at Northwood, when CdM scored just before halftime then scored three more times in the second half. This time, the Sea Kings had to settle for a single second-half goal.

It happened off a booming free kick into the box in the 59th minute. Senior Emily Krebs' initial shot was blocked by Northwood goalie Brigid Overton, but CdM sophomore Elise Roche scored on the rebound.

Defense from junior goalie Kendall Mulvaney (two saves), Hunter, senior Alexa Mamatas and sophomore Brynn Motal helped CdM record its sixth shutout of the year. Middleton said Mamatas has committed to the University of Arizona, and Krebs has committed to Vasser College.

CdM will again be short-handed when it plays host to University at 11 a.m. Saturday at Jim Scott Stadium.

"It might not have been the prettiest game, but we got the job done," Karsten Sigband said. "[Westrup's injury] hits home to me, because I tore my ACL. I know how tough that is, but we'll see. You can't really know anything until you get the MRI back. Hopefully it isn't anything too serious and she'll be back as soon as possible."

matthew.szabo@latimes.com

Twitter: @mjszabo