Arizona fans had high expectations for the defending champions entering this season, but it would have been nearly impossible for the Wildcats to improve on last season’s success.

Wednesday’s three-game sweep to Oregon State at Hi Corbett Field brought many Arizona fans back to reality. The sweep by the Beavers also established their pitching staff as a dominating force that has made them early favorites of the Pac-12 conference.

Arizona head coach Andy Lopez said he believes the pitching staff must be stronger than the offense. Nearly all the teams at the top of the conference are led by their pitching staff, which is why Arizona currently sits in the middle of the Pac-12’s power rankings.

Oregon State (19-1, 3-0 Pac-12)

Fresh off a sweep of the Wildcats, the No. 4 Beavers have reached the high ranking behind their strong pitching staff. Led by Friday night ace senior Matt Boyd (4-0), Oregon State posts the nation’s lowest team earned run average (1.59). The Beavers also rank in the top-10 in hits allowed per nine innings, one behind UCLA.

Before this past weekend’s sweep in Tucson, Oregon State also demolished a then-No. 22 San Diego State team on the road in a four-game series. The Beavers outscored the Aztecs 22-2 in the four games.

However, what makes Oregon State valuable is that it relies heavily on its pitching staff. Currently ranked 48 in the country in scoring (6.7 runs per game), the Beavers could slip in the rankings if their pitching staff can’t maintain their dominance. But for now, the Beavers are hot.

UCLA (15-3, 3-0)

No. 11 UCLA might be the most complete team in the conference. The only characteristics that separate UCLA from Oregon State are that the Bruins have lacked consistency and started the conference season off against an unimpressive Washington team.

Similar to the Beavers, UCLA’s top-notch pitching staff is far more threatening to opposing teams than its offense. Junior Adam Plutko (2-0) fronts the staff and is an early candidate for conference pitcher of the year.

Stanford (10-5, 0-0)

A consensus top-10 team entering the season, the Cardinal has quickly fallen out of the top-25 due to injuries to two of its stars. Junior starting pitcher A.J. Vanegas sustained a back injury during the summer and has yet to see the mound in 2013. Junior outfielder Austin Wilson has missed all but the first game of the season after injuring his elbow. Out of high school, Vanegas and Wilson were drafted in the seventh and twelfth round of the MLB Draft, respectively, but now the two are first-round prospects.

Incredibly, Vanegas and Wilson aren’t the only first-round prospects on Stanford’s roster. Senior starting pitcher Mark Appel and junior first baseman Brian Ragira are also high on scouts’ lists.

However, Appel and Ragira have struggled in 2013 due to their injuries. Despite posting a 1.20 earned run average, Appel can’t get any run support and is 2-2 on the season. Ragira has had a steady bat early into the season but hasn’t had many plate appearances with runners in scoring position.

Arizona (15-8, 0-3)

The Wildcats’ offense has recovered well even after losing five starters from last season’s national championship team. Powered by arguably the conference’s best hitters, third baseman Brandon Dixon and 2012 Pac-12 Batting Champion Johnny Field, the Wildcats are averaging just over seven runs per game, first in the Pac-12.

But the loss of Friday night ace Kurt Heyer to the major leagues may prove more devastating than the five offensive players. Arizona’s pitching staff has given up 99 runs, 10th most in the conference. 32 of those runs have been charged against new Friday night ace Konner Wade and Saturday starter James Farris. Heyer excelled because he set the tone for the rest of the series. Though Wade has faltered early, he shined in the 2012 tournament.

1. No. 4 Oregon State (19-1, 3-0 Pac-12)
This week: home vs. ASU
Week one: W 6-2, W 4-3, W 8-4, at Arizona

2. No. 11 UCLA (15-3, 3-0)
This week: vs. California
Week one: W 3-2 (15), W 5-0, W 3-0, vs. Washington

3. No. 13 Oregon (15-6, 2-1)
This week: vs. Arizona
Week one: W 5-2, W 8-4, L 5-3, at USC

4. No. 20 ASU (12-4-1, 1-2)
This week: at Texas Tech, Oregon State
Week one: L 15-4, W 4-1, L 11-8 vs. Washington State

5. Arizona (15-8, 0-3)
This week: at Oregon
Week one: L 6-2, L 4-3, L 8-4, vs. Oregon State

6. California (15-7, 3-0)
This week: at San Jose State, UCLA
Week one: W 9-5, W 9-5, W 6-4, at Utah

7. Stanford (10-5, 0-0)
This week: vs. Utah
Week one: Bye

8. Washington State (11-7, 2-1)
This week: vs. Gonzaga, Brown
Week one: W 15-4, L 4-1, W 11-8, at ASU

9. USC (8-12, 1-2)
This week: at Louisville, Washington
Week one: L 5-2, L 8-4, W 5-3 vs Oregon

10. Utah (8-9, 0-3)
This week: at Stanford
Week one: L 9-5, L 9-5, L 6-4, vs California

11. Washington (4-14, 0-3)
This week: vs. Portland, USC
Week one: L 3-2 (15), L 5-0, L 3-0, vs UCLA

– Luke Della is a journalism junior. He can be reached at sports@wildcat.arizona.edu or via Twitter @LukeDellaDW.