BYU will play in an elimination game at 2 p.m. MDT Friday against Sacramento State, which lost 10-0 to regional top seed Stanford in the other game Thursday.
The Cougars started their regular No. 2 pitcher, Brady Corless, and the Titans jumped on him quickly. Scott Hurst led off with a double and later scored on a throwing error. Dillon Persinger singled, stole second and scored on a single by Timmy Richards to make it 2-0, then Richards scored on a single by Hank LoForte as the Titans took a 3-0 lead.
The Titans extended the lead to 4-0 in the third inning on a sacrifice fly, chasing Corless before Hunter Cullen homered to make it 6-0 in the third off BYU reliever Jordan Wood. Cal State Fullerton added one more run in the fourth, two in the fifth and four more in the eighth.
Cullen gave Cougars pitching fits, finishing 3 for 5 as Cal State Fullerton finished with 22 hits overall. Six pitchers appeared for BYU, none going more than Corless' 2 2⁄3 innings to start the game.
"We were going to have to play perfect baseball to stay with them," Littlewood said. "Honestly, I just didn't think we pitched very well. We left a lot of pitches over the middle of the plate today, which we didn't do last weekend."
On the other side, Seabold was dominant early, retiring 12 of the first 13 hitters he faced. BYU's first run came in the fifth inning on a two-out double by Nate Favero that scored Brock Hale.
Colton Shaver ripped a solo home run to left in the seventh for the Cougars off Titans reliever Jake Pabich.
Hale finished with three hits for BYU, and Favero had two hits.
BYU now finds itself in a similar situation to the West Coast Conference tournament, when the Cougars lost their opener to Loyola Marymount. BYU then won four consecutive games to earn the tournament championship and NCAA automatic bid.
"At this point in the season, I just stay out of their way and let them play," Littlewood said. "There's not a whole lot we can do. The worst thing you can do is get on them, be upset with them, be disappointed in them because they've played 60 games of outstanding baseball. So you just go out there and let them play. I think you'll see a different team tomorrow from us."