The 2003 Seattle Mariners are known for a couple things. One of those is that they managed to use five starting pitchers for the entire season. All five members had either 32 (Ryan Franklin, Joel Pineiro, Gil Meche) or 33 starts (Jamie Moyer, Freddy Garcia). It wasn't actually that good of a rotation -- their 3.92 collective ERA belied a 4.67 xFIP -- but they were healthy and there's almost always value in avoiding needing the dreaded sixth (or worst) starters.
I also don't think it gets enough credit for how unlikely it was given the people involved. Gil Meche had basically not thrown a professional pitch since 2000. Jamie Moyer was 40 years old. Ryan Franklin had started 12 Major League games in his career prior to 2003. Joel Pineiro was moving to the rotation full time and Freddy Garcia was a home run-serving nut case. That's the group that combined to never miss a start? Improbably bizarre.
Side note: Moyer and Garcia were traded for and Franklin, Meche and Pineiro were all Mariner draft picks. Not one of them was a free agent signing.
Until about 30 minutes from now, the 2011 Mariners were on that same ground, except way better because the starters this year have all been legitimately fantastic. They are the last remaining hold out in baseball and will now join seven other teams who have used six starters. The Oakland Athletics and Colorado Rockies have used 10.
Pour out some champagne, 2003 rotation. You survive another year.