It can often alter a career by several degrees. Some pitchers excel using only the fastball. Rare pitchers can compete only with their dexterity and control. Nobody succeeds without knowing the science. That's why I mistrust young pitchers.
Young guys are dumb.
Their talent is measured by a single standard, which is constantly declining. That's the trick. Unfortunately, any significant statistical measure of pitching skill is polluted heavily by context and sheer luck - saves, wins, Losses, earned runs, hits allowed, homeruns, strikeouts and walks. All of these results are the product of the pitcher's skill, managerial tendencies, team offense, team defense, skill of the opposing pitchers, skill of the opposing defense and offense, visibility, park effects, weather effects and umpiring. It's just too many variables.