NORMAN, Oklahoma - No. 4 seed Oklahoma softball (55-3) opens play at the 2018 Women's College World Series Thursday at 1:30 p.m. CT against No. 5 Washington (49-8) on ESPN. 

The back-to-back defending national champions, the Sooners are making their seventh WCWS appearance in the last eight years and 12th trip overall.

This will be the fifth time the Sooners face the Huskies in the WCWS and 10th postseason meeting overall. The two programs last met at the 2017 WCWS, with OU claiming a 3-1 victory. 

In their second game of the double elimination tournament, the Sooners will face either No. 1 Oregon (52-8) or No. 8 Arizona State (48-11). A win over Washington would have OU play on Friday at 6 p.m. CT, while a loss would see Oklahoma play its second game Saturday at 11 a.m. 

All-session tickets are sold out, as are all single-sessions except for session 1. A limited number of standing room only tickets will be made available for each sold out session. They will be made available at the stadium on the day of the respective session. Fans can also look for tickets on NCAA.com/Exchange, the NCAA-approved secondary ticket marketplace.