The Tampa Bay Rays won 100 games in 2021, proof that a great starting rotation need not be necessary in this era of baseball, at least not with every team. It's not that the Rays' rotation was terrible -- it finished a respectable sixth in the American League with a 4.08 ERA -- but the team had obvious holes. Consider:
The Rays' top two starters in terms of innings pitched were Ryan Yarbrough (5.11 ERA) and Michael Wacha (5.05 ERA).
Rays starters finished 14th of the 15 AL teams in innings pitched.