PCFRASER: 27 must be the lowest score for 9 holes ever.
It's not the lowest, but it's pretty close. Regardless, that's some fantastic playing by Sergio!
Corey Pavin shot 26 on the front nine in the 2009 US Bank Championship. (8-under) (lowest 9-holes in a PGA event)
Jason Bohn shot 26 on the front nine in the 2001 Bayer Championship on the Canadian Tour. (9-under) (he had a 32 on the back for a 58 total)
However, Jamie Kureluk carded the lowest professional 9-holes that I know of, an incredible 25 on the back 9 in the 2010 Alberta Open. (11-under) (for those interested...Carnmoney's a par 71, rated 70.6, and sloped 135)
Hmm...maybe the scores on here aren't so wacky after all eh? ;-)