Irvin underwent Tommy John surgery earlier this year and will miss the entirety of the season.
"We're moving on. We have no choice, and we think we have guys that can be next man up so to speak," Oregon coach George Horton said Wednesday."
"Time will tell. It's hard to replace the 12 wins and the potential All-America," Horton said. "We'll just have to see how seriously that will effect us. Hopefully it won't."
Spencer has made eight career starts and holds a career 6-2 record. Included in the outings was the lone no-hitter since the program was reinstated. The no-no came against Portland in 2012.
"What you hope is that you're not playing musical starters. Because what that usually means is that you're losing games," Horton said of the rotation. "Until [Spencer] proves differently, then yes [he'll remain in the rotation], and we don't expect him to prove differently."
Irvin is expected to make a full recovery before the beginning of next season, and according to Horton has managed the situation with great character.
"He's handled it probably better than coach Horton. I had my head up my rear end a little bit more than he did," he said. "He sees it as a bump in the road. He's very happy with how the surgery came out."
Ducks open this weekend in Hawaii
Hawaii hosts Oregon for a four-game series beginning Friday. The Ducks opened the past three seasons with the Rainbow Warriors, winning 9-of-12 games in Honolulu.
The goal is once again to begin the season on the right foot, as they did last year with a four-game sweep. Horton hopes doing so will help instill confidence and lead to a different outcome than the past two postseasons.
"One of our mission statements is to start fast and finish strong. What we haven't' been able to do is finish strong," he said. "The last couple years especially we have not finished the job. We've put ourselves in position to have a really spectacular year, and unfortunately we haven't finished.
"We'd love to start fast. That keeps you on the board, that keeps you in the hunt, and then improve along the way to give us a chance to finish strong."
Horton will start Thorpe, Spencer, Krook and Jeff Gold over the four games.
Frosh Kruger to start at catcher
Like in recent years, Horton will rely on multiple backstops. And just like last year a freshman will get the first crack.
Horton explained that once again, "there's not a lot of gap between the three of them," and that having multiple quality pitchers over the course of a 60 game season can be a real advantage.
"If we said who is the one guy who will catch this game to win this game tomorrow, it would be Jack Krueger," Horton said.
"He's a pretty special kid. He's got leadership written all over him. He got appointed into West Point Academy. Guys don't get into West Point Academy without having great character traits."
Kevin Minjares has been handed the difficult task of replacing program cornerstone J.J. Altobelli at shortstop. Minjares, a 5-foot-6 senior, won't be asked to "hit a lick", according to Horton, but his defense might prove vital.
Reed spent the last two season as starter, but will embrace the closer role this season. Cleavinger joined Irvin as a freshman All-American recipient last year, and is listed among the NCBWA Stopper of the Year watch list to begin 2014.