What's the difference between winning a national championship and being left out of the NCAA tournament altogether?

The answer for the Arizona Wildcats is apparently four regular season wins.

Despite a 34-21 record and an even 15-15 campaign in the Pac-12, the Wildcats weren't one of the 64 teams selected for the postseason in the bracket released Monday morning.

The 2012 team went 38-17 in the regular season and then of course went on to win 10 straight games in the postseason and win the College World Series.

The 2013 Wildcats won't get a chance to defend that championship.

"Thirty eight (wins) and we won a national championship last year. We have 34 today and we're not good enough," Arizona coach Andy Lopez said. "It's life, so you move on and get better. You have to take care of it on the field."

And in the selection committee's mind, the Wildcats didn't.

The major factors that seemed to hurt the UA were:

• An RPI of 58, which would have been the worst mark to receive an at-large bid this year. UC-Santa Barbara, at No. 55, was able to sneak in.

• A 0-9 record against Oregon State, Oregon and UCLA, the Pac-12's three best teams.

• An 8-18 mark against RPI top 100 teams

• A 6-11 record away from Hi Corbett Field.

• Five teams (Central Arkansas, East Tennessee, Liberty, Towson and San Diego State) that won their respective conference tournaments to steal bids from bubble teams like the Wildcats. None of those teams were candidates for at-large bids in conferences that went from apparent one-bid teams to two because of the upsets.

"It's a tough moment for all of us," junior center fielder Johnny Field said. "We didn't play as well we wanted to all year, but we really thought we played well enough down the stretch to sneak in."

The Wildcats won five of their last six games to crawl back into contention and Lopez thought that would be good enough.

On Monday, he still did.

The Pac-12, ranked as the third-best conference in the nation in the RPI, had just four teams - Oregon State, Oregon, UCLA and Arizona State - qualify for the postseason. Lopez thought the Wildcats and Stanford had good enough résumés to also get in.

The veteran coach, who spent seven seasons coaching in the SEC at Florida, thought that conference was shown too much respect, getting nine teams into the field. The Gators, with a 29-28 record, were one of the nine to get in.

"I lived in the Southeastern Conference for seven years and in the Southeastern Conference, you get rewarded for having an average year, aka Florida, and in the (Pac-12), you don't get rewarded, you get punished," Lopez said. "There's no way just four teams from the Pac-12 should be in there. Florida lost nine of their last 11 conference games. I mean, are you kidding me?

"Thirty-four wins in the SEC and you're probably hosting. Thirty-four wins in the Pac? 'Hey, have fun running your summer camps.' "

Now that the Wildcats are officially out, there are three series' that will haunt Lopez the most are:

• Losing two of three at Stanford, including blowing a 3-0 lead in the opener

• Dropping two of three at home to Washington, ranked No. 93 in the final RPI.

• Opening the season with three home games against Coppin State, ranked No. 290, rather than a three-game series at Auburn, which was the plan until the Tigers canceled before the season.

"Based on the magical SEC, even we have had gone to Auburn and lost three games, our RPI would have been better," Lopez said. "Washington played exceptionally well the second half of the season and Stanford was just a rough series."

The players were less concerned with the reason they were left out and instead just disappointed their season was over.

Brandon Dixon, who wrapped up the Pac-12 batting title on Sunday and is contention for the conference's player of the year, which will be announced this week, wasn't ready for his Wildcats career to end.

Eligible to be selected in next month's Major League Baseball draft, Dixon will likely sign with a professional franchise at some point this summer.

"I was expecting to play this weekend," Dixon said. "We just have to move on."

On StarNet: View photos from the 2013 UA baseball season at azstarnet.com/gallery

Contact reporter Daniel Berk at dberk@azstarnet.com or 573-4330. On Twitter @DSBerk.