The mark of a truly great starting pitcher used to be 300 wins. It was considered a milestone on par with hitters getting 3,000 hits or 500 home runs. However, due to developments in the strategy of the game and more conservative use of pitching arms to avoid injury, 300 wins is no longer a reasonable expectation of a great pitcher. There are very few pitchers today that appear to have a chance of getting 300 wins, even with great luck. A starting pitcher may not get 300 wins for a very long time, especially not in the current baseball environment.
The primary factor in the decline of the 300-win season is teams’ increased use of the bullpen. The starting pitcher is pitching less innings as managers more frequently pull them out for relievers. Most teams have 6 or 7 relievers: long relief pitchers for when a starter is knocked out early, middle relief pitchers for the 7th or 8th innings, and closers for when the game is close in the 9th inning. In a close game a starting pitcher will typically be pulled out for a fresh arm, preferably a lefty if the batter is left-handed, and a righty if it’s a right-handed hitter. There is a lot of specialization: for particular innings, game situations and hitter handedness.
Batting averages against a starting pitcher go up dramatically every time through the lineup because the hitters have seen more pitches from him that day. Managers know this and favor relievers for this reason as well. Throughout the major leagues, heavy use of the bullpen is the new strategy of choice.
The other main reason that pitchers won’t get 300 wins is the desire of teams to avoid overworking pitchers. The fruits of this desire are the five-man rotation and increased focus on pitch count to prevent injury and keep starting pitchers at their most effective pitching. Managers are wary of allowing a starter’s pitch count to go very far over 100 pitches. There is the fatigue factor; pitchers get tired and their control and velocity decreases. But the focus is also long-term. Teams don’t want their pitchers to get injured. That could mean long stays on the disabled list or surgery, like Tommy John surgery, where they could be out for a full year or longer. Younger pitchers especially are carefully monitored, so that they are not injured during their crucial developmental stage.
The standard five-man rotation prevents pitchers from starting as many games as they used to and pitching as many innings. The four-man rotation began to be abandoned in the 1970s as teams realized that it would keep their pitchers healthier. Although a four-man rotation worked for decades and may not have led to many more injuries, a five-man rotation is now the standard and starters make an average of 4 less starts per season than they did in the 1970s. Over a 20-year career, that adds up to 80 less starts, which is 80 less chances for a win!
At the moment, there are very few MLB pitchers on track for 300 wins. CC Sabathia seems to have a chance with 214 wins at age 34. Say he lasts until he’s 40, he needs to average just under 15 wins a season. Clayton Kershaw is an impressive young pitcher; at 27 he has already won 3 Cy Young awards! He has 114 wins so far, but he has a long road ahead of him. Fun fact: in 2016 the Los Angeles Dodgers payed Clayton Kershaw $34,571,429, the highest salary a player has earned in a season in the history of Major League Baseball. There are a few others who stand a chance, but every MLB player would need incredible consistency and longevity to get to 300 wins. I doubt any of the current starting pitchers will make it, or any future pitchers for many, many years.