INDIANAPOLIS (AP) -- Illinois never considered itself the underdog against Ohio State (No. 23 ESPN/USA Today, No. 22 AP).
Nevermind the Buckeyes' top seed. The Fighting Illini fully expected to win their Big Ten tournament quarterfinal game Friday night.
Rebecca Harris scored 22 points, and Illinois beat the Buckeyes 64-58. Lori Bjork scored 14 points and Jenna Smith added 13 for the ninth-seeded Illini (18-13), who reached the semifinals for the first time since 2001.
"The seeding means nothing to us," Harris said. "We know we can beat any of these teams because we've seen them already. If we were the underdog, then I guess it was an upset."
Illinois will play Michigan State on Saturday. The Spartans beat Minnesota 56-51 Friday night.
Illinois gained confidence by beating the Buckeyes 68-64 on Jan. 31 to split the regular-season series. The Illini have won three in a row under first-year coach Jolette Law, but know they need two more victories to clinch their first NCAA Tournament bid since 2003.
"I tried to mute my celebration a little bit, trying to save energy for the next two games," Bjork said.
Marscilla Packer scored 15 of her 19 points in the second half for Ohio State (22-8), which lost its tournament opener for the first time in school history.
Jantel Lavender, the conference's co-player of the year, finished with 14 points and 12 rebounds for the Buckeyes. The freshman took just eight shots, which bothered Ohio State coach Jim Foster.
"I think we rushed at the guard positions and weren't patient enough to take advantage of our post presence," he said.
Smith said the plan was to keep the ball out of Lavender's hands.
"Lavender is very strong, so we kind of sagged off the other posts and dared them to beat us," she said. "With [Lavender], we just had to body-up on her and be real physical."
Bjork made a 3-pointer to give the Illini a 54-43 lead with just over seven minutes to play, but Packer scored 11 points in four minutes, including a 3-pointer that cut Illinois' lead to 58-54.
"Marscilla is that kind of streak player who can get unconscious and score a lot of points in a short amount of time," Foster said.
Illinois led 60-57 and had the ball in the final minute, but Ohio State took possession on a steal by Packer. After a flurry of missed shots, the Buckeyes gained control and called timeout to set up with 21.5 seconds left and the shot clock off.
Ohio State's Ashlee Trebilcock missed a 3-pointer, but teammate Tamarah Riley was fouled on the rebound. She made the second of two free throws to trim Illinois' lead to 60-58.
Bjork made two free throws with nine seconds left, then Harris made two more to provide the final margin.
Ohio State led 16-14 in the first half before back-to-back 3-point plays by Harris and Smith gave the Illini a 20-16 lead with 7:22 left.
Illinois remained in front until the final seconds of the first half.
The Illini had possession and a 27-25 lead when there was a scrap for the ball. Ohio State came up with it, and a Buckeye player threw a long pass toward the right corner. Alison Jackson barely caught up to the ball, but she gathered it and flung it toward the basket in a single motion. The 3-pointer banked in as time expired to give the Buckeyes a 28-27 lead.
Illinois' 15-6 run to begin the second half stopped the momentum the Buckeyes had built.
Ohio State led the conference in scoring during the regular season, and Illinois topped the league in scoring defense. Illinois' slower tempo and grind-it-out style won out against the Buckeyes.
"It was the pace we wanted," Law said. "We knew they were going to come out and try to get their transition, and that was one of the keys -- we had to stop their transition. The pace was in our favor tonight."
Now, the Illini are trying to stay focused. They know that no team seeded lower than fifth has won the tournament.
"We're trying to make history here," Law said. "Not looking past the next opponent, we're trying to do it game by game, step by step."