How Bullpen Usage Changed Baseball

For most of baseball history, the bullpen was where you stashed the pitchers who couldn’t start. Today it’s often where games are won. The way teams use relief pitching has changed more than almost any other part of the sport in the last 50 years — and understanding that shift explains why no modern staff leans on one arm the way old teams did.

From the scorebook — In the 1970s, hundreds of complete games were thrown across MLB every season. In recent full seasons the leaguewide total has fallen to just a few dozen. The nine-inning start didn’t get harder; teams simply decided fresh relievers were the better bet.

The death of the complete game

Once, a good starter was expected to finish what he began. Twenty or more complete games in a season was routine for an ace, and staffs like the 1971 Orioles built their identity on it. That world is gone. As analysts documented that hitters improve dramatically the third time they see a starter in a game — the “times through the order” penalty — managers grew far quicker to go to the pen. The complete game went from a badge of honor to a near-extinct event, with the leaguewide total in a full modern season now counted in the dozens rather than the hundreds.

The rise of the one-inning closer

Relief specialization has a clear turning point. The save became an official statistic in 1969, giving the late-game reliever a number to chase. But the modern closer — a dominant arm held back for the ninth inning of a lead — was really shaped in the late 1980s, when manager Tony La Russa deployed Dennis Eckersley in tightly defined save situations for the Oakland A’s. The role stuck. By the time Mariano Rivera retired as the all-time saves leader, the ninth-inning closer was as fixed a position as shortstop.

Leverage: the smarter question

The next wave of thinking pushed past the save. Analysts pointed out that the highest-stakes moment of a game often isn’t the ninth inning — it can be a bases-loaded jam in the seventh. That idea, leverage, argues your best reliever should pitch when the game is most on the line, not when the save rule says so. Postseason baseball has embraced it: teams like the 2016 Cleveland club rode a single elite reliever, Andrew Miller, across multiple innings in whatever spot mattered most. “Bullpenning” a playoff game — stringing together relievers instead of asking a starter to go deep — became a legitimate blueprint.

The opener flips the script

The most radical change came in 2018, when the Tampa Bay Rays, short on rotation depth, started using a reliever to begin games. This “opener” faces the top of the order once, then gives way to a “bulk” pitcher who works the middle innings. The logic is pure matchup math: the opener neutralizes the best hitters early, and the bulk arm never has to face the lineup a punishing third time. Other teams copied it, and the line between “starter” and “reliever” blurred for good.

What it means for a perfect season

All of this reinforces the ceiling that defines 162-0. Bullpen usage evolved precisely because no rotation can cover a full season on its own — the fourth and fifth starters are beatable, and fresh relievers are how teams paper over that gap. But a bullpen has limits too: relievers get overworked across a daily grind, and a taxed pen on the back end of a road trip is a worse team. Run prevention over 162 games is a depth problem no strategy fully solves, which is a big part of why 162-0 is effectively impossible. If you’re weighing how to build a staff for a run, see the best era to draft in.