CORVALLIS — This Civil War series is worthy of a third chapter.

That could happen in the Pac-12 Tournament championship game on March 10 in Las Vegas.

But will Ruthy Hebard be a part of the Ducks' postseason run?

That was the question coach Kelly Graves didn’t have an answer to after No. 2 Oregon’s 17-game winning streak ended with a painful 67-62 loss to No. 12 Oregon State on Monday night in front of a sold-out crowd of 9,301 at Gill Coliseum.

Hebard left the game with an injury in the second quarter. The junior forward had eight points and four rebounds in 13 minutes before limping to the bench and having her right knee wrapped in ice.

“Don’t know; doesn’t look good,” Graves said of the initial diagnosis for Hebard, the reigning national power forward of the year. “We’ve got a lot of season left to play for and obviously we were good enough to have a chance to get it done without her. We’ll see. …

“She’s not walking healthy. I don’t know the severity.”

The Ducks (24-2, 13-1) and Beavers (21-5, 11-3) split the back-to-back meetings in front of a combined 21,665 paying customers. With four games remaining in the regular season, the rivals are the top two teams in the Pac-12 standings. Oregon is alone in first place and Oregon State is tied with Stanford for second.

Sabrina Ionescu drew a foul behind the 3-point arc and made all three free throws to get the visitors within 63-62 with 7.2 seconds left.

The national player of the year candidate had a chance to dribble down and force overtime with a 3-pointer after two free throws by Destiny Slocum, but Ionescu was called for traveling with Aleah Goodman applying pressure as she caught the in-bounds pass.

Ionescu scored 21 points on 9-for-25 shooting (0-for-6 on 3-pointers).

“I thought our defense was on point from the beginning,” Oregon State coach Scott Rueck said after improving to 15-3 against the Ducks. “Their overwhelming energy and will to win was elite tonight.”

Oregon, which was second in the NCAA in field-goal percentage (52.4) and first in 3-point field-goal percentage (44.1), finished 24-for-67 (35.8 percent) shooting, including 5-for-22 (22.7 percent) behind the arc.

“I thought we gave ourselves a chance to win under really difficult circumstances,” Graves said after the Ducks lost their 10th consecutive game in Corvallis dating back to Jan. 9, 2010. “The bottom line is you’ve got the best shooting team in the country and you shoot 35 percent. That’s not going to win many games. A lot of those (shots) were forced and out of sync.

“Obviously without Ruthy we had to kind of draw up some stuff on a napkin and go.”

Goodman scored 22 points and Slocum added 20 points on a combined 14-for-27 shooting (51.9 percent) to lead Oregon State to the upset.

Slocum broke a 52-52 tie with a jumper in the lane and a clutch 3-pointer to give the Beavers a 57-52 lead with 1:52 remaining.

Taylor Chavez answered with a 3-pointer, but Oregon State went 8-for-8 at the free-throw line in the final 14.4 seconds to ice the win.

“We were right there on Friday night and we knew we didn’t play our best game,” Goodman said of the Beavers’ 77-68 loss at Matthew Knight Arena. “That was huge motivation for us.”

After making a left-handed layup in traffic to tie the score and then a jumper to give Oregon a 52-50 lead with 6:23 remaining, Ionescu missed an uncontested layup with a chance to give her team a late four-point cushion.

Maite Cazorla came up with a timely block of 6-foot-8 center Joanna Grymek to keep the Beavers from retaking the lead until Slocum’s heroics.

“I feel for her,” Graves said of Ionescu, who played all 40 minutes, finishing with seven rebounds, four assists and two turnovers. “She played hard, it just wasn’t her best shooting night. She’s one of the best players in the country for a reason. She’ll learn from this.

“Believe me, this will eat at her and drive her this next weekend and the following weekend after that. That’s who she is.”

With Hebard remaining on the bench after going through warm-ups before the start of the second half, Satou Sabally attacked the paint and completed two old-fashioned three-point plays to get Oregon within 41-36 midway through the third quarter.

A basket by Ionescu tied the score 45-45 before five unanswered points from Goodman.

Erin Boley splashed a 3-pointer to get the visitors within 50-48 entering the fourth quarter.

“We had some pretty good looks down the stretch,” Graves said. “They didn’t fall for us tonight.”

The Ducks, who trailed by as many as 11 points in the first half, cut the deficit to 33-27 at the intermission despite losing Hebard and shooting 33.3 percent from the field.

A 3-pointer and a driving layup by Slocum gave the Beavers a 31-20 lead with 3:10 remaining in the second quarter.

“The game changed of course when Ruthy went down,” Rueck said after countering Oregon’s smaller lineup with his own guard-heavy group. “It changed to a chess match that neither of us had prepared for.”

Graves is hoping his queen of the paint will be healthy enough to return as the Ducks try to repeat as Pac-12 champions and lock up the No. 1 seed in the Portland Regional.

“We’re going to pray, hope that she is better,” Graves said of Hebard. “We have a great training staff.”