Scottie Scheffler enters this PGA Championship at Aronimink as the top-ranked player in the world at at the height of his powers. He’s also the defending champion at this event, and with that comes a shot at history. Repeat winners don’t come along often at the PGA, perhaps because it changes venues each year. Or perhaps because the field is so deep . And maybe also because it’s just extremely tough to win majors, much less the same major two years in a row. In modern history, only two players have won back-to-back PGA Championships: the most recent was Brooks Koepka in 2018 at Whistling Straits and 2019 at Bethpage Black . Tiger Woods also won repeat PGA titles, achieving the feat in 1999 and 2000 and then again in 2006 and 2007. For repeat PGA winners in the modern era, that’s it. Koepka and Woods are the entire list. It gets lost a bit in history, but for several decades the PGA Championship was a match-play event. Back in that era, it produced a handful of back-to-back winners.…