Two innings into the season, the Oregon baseball team lost its ace and the Ducks have struggled to establish roles for their pitchers ever since that opening day at Texas Tech.

Kenyon Yovan, a two-time all-Pac-12 selection, has not pitched since the Feb. 15 opener. It remains uncertain if he will pitch again for the Ducks (24-22, 8-13), who host No. 12 Oregon State (31-14-1, 17-4) in a three-game series beginning at 7 p.m. Friday at PK Park.

Ryne Nelson, Cole Stringer and Robert Ahlstrom have all missed starts due to injury as the Ducks have used six different starting pitchers in 21 Pac-12 games while ranking last in the conference with a 7.88 ERA in those contests.

“Jekyll and Hyde, but more Hyde than Jekyll,” Oregon coach George Horton noted.

Oregon opened the season with two of the top 25 pitching prospects in college baseball, according to Baseball America, but Yovan and Nelson have combined for only five starts.

Yovan developed blood clots in his right palm and later had numbness in a finger that has kept him from being able to even throw a bullpen session in practice.

Nelson suffered a heel injury early in the season and was moved to the bullpen where he has remained all season as Horton tries to pick spots to use the 6-foot-3 right-hander with a fastball that nears 100 miles per hour. After throwing 12 2/3 scoreless innings over seven appearances, Nelson has allowed four earned runs in his last three outings and been the losing pitcher in each of those games.

After missing last season due to injury, Stringer missed a couple of starts in March but returned to the rotation four weeks ago and has a 6.58 ERA with a 1-1 record. Ahlstrom, a junior-college transfer who prepped at North Eugene, was slated to pitch in relief before becoming Oregon’s most reliable starter at 5-4 with a 3.83 ERA.

“We’ve had crazy luck this year with Kenyon going down and being out longer than expected and then Nelly having to go to the pen,” Ahlstrom said. “People have been getting bounced around so it is hard to find a set routine. We have to overcome it as best as we can and adapt, but it has been difficult.”

Ahlstrom missed two starts due to illness before returning to allow four earned runs in 6 1/3 innings at Arizona on Saturday.

“I felt real good,” he said. “It was a real hot and difficult atmosphere but just being out on the mound competing again was cool. I felt a little rusty taking a couple weeks off, but as the game went on I felt like I was doing better. I got tired quicker, but I am almost back to where I was which is a good sign.”

Cullen Kafka has been in the rotation for Pac-12 play, but allowed 11 runs, including five earned, in one inning Sunday as his ERA rose to 5.00 with a 5-4 record. Brett Walker, who is 1-1 with a 5.79 ERA, has started three conference games.

Kolby Somers, who was in Oregon’s starting rotation most of his freshman season, has pitched mostly in relief as a sophomore but made one start in Pac-12 play along with freshman Tyler Frazier.

The Ducks haven’t solidified a closer with Nico Tellache leading the team with six saves while Nelson has three and both Walker and Somers have a save. Nelson is Oregon’s only regular reliever with an ERA under 5.00 on the season.

“We’ve thrown a lot of things at the wall and nothing has stuck,” Horton said. “There has been a bright spot or two here and there, but overall it has been crummy.”