1. Zach Greinke, Royals Pitcher
Greinke is 4-0 with a 0.00 ERA. Four starts and no earned runs given up yet. Greinke is the most dominant pitcher in the majors right now but he plays for the Royals so not a lot of fans know about him or how good he is.
2. Chad Billingsley, Dodgers Pitcher
Billingsley is also 4-0 with a 2.05 ERA. He has pitched at least six innings in each of his four starts and is coming off a dominating pitching performance against the Astros last week. His next game will be Tuesday against the woeful Giants offense. Billingsley struck out 11 Giants in a game earlier this season.
3. Johan Santana, Mets Pitcher
Santana is 3-1 with a 0.70 ERA. The Mets are struggling this year but they know they have a good chance to win when Santana is on the mound.
4. Felix Hernandez, Mariners Pitcher
Hernandez is 3-0 with a 3.12 ERA and is coming off an impressive start against the Rays. He pitched seven scoreless innings in that game and struck out seven. He is fourth in the AL in strikeouts with 27.
5. Erik Bedard, Mariners Pitcher
Bedard is 2-1 with a 2.08 ERA for the Mariners, and is ranked third in strikeouts in the AL with 29. He is holding left-handed hitters to a .174 batting average.
Some other pitchers that I did not include in this list but are worthy candidates include Giants pitcher Matt Cain, and Reds pitcher Aaron Harang.