OF Casey Martin

Martin has turned in an eye-popping batting average of .373 with an OPS of 1.072. Still, "only" 5 HR and 14 RBI may hold him back compared to other candidates.
SP Jean-Phillipe Te'treault

Turning (much too soon) to pitchers in the JL, we start with the Te'treault. Jean-Phillipe has compiled a 6-3 record for Pheonix while delivering a 3.46 ERA and striking out 73 batters in 78 IP. His WHIP is 1.54 and that could be improved, but it has been an impressive campaign so far for Te'treault.
SP Steven McCullough

McCullough has also compiled a 6-3 record in his rookie year, but he has done so while sporting an impressive 2.71 ERA and a WHIP of 1.26. His strikeouts are pretty low and his walks a little high, but that makes his WHIP even more impressive.
I completely overlooked California's stock of young arms because I thought they belonged to Calgary.
P Michael Duran

Michael Duran starts the cascade of rookie pitchers that have been stockpiled on the West coast. In 57.1 innings, Duran has delivered a 3-3 record. This while compiling a 3.77 ERA and a miniscule WHIP of 1.06. He simply mows down hitters with 62 strikeouts in those 57 innings and 15 walks. That's cheese, my friends.
P Steve Taub

Up next for Cali is Taub. So what has he delivered? Only an 8-2 record with a 2.85 ERA and 1.10 WHIP. Those are All-Star numbers right there. He's only walked 16 batter in his 98 IP, but has only rung up 60.
P Oscar Funke

The parade of arms continues for California. Next up is Funke. In 90 IP, Funke's record is 7-4. He has logged a pretty good ERA of 3.6 and a WHIP of 1.44. He's got great numbers for a rookie, but he has to be shaking his head that he's probably the 3rd best newcomer just on the pitching staff out West.
That's all I can dig up for rookies in the JL. Who did I overlook? Who's the frontrunner?