Killebrew walked 145 times in 69,and led the AL with a .427 OBP. It's not plate discipline that limits RBI. Killer played 162 games that year, and got 709 PAs. That, coupled with 49 dingers and a .584 SLG got him the ribeyes. In the year Sosa drove in 160, he walked 116 times, .437 OBP...with 711 PAs. Its those 700-ish PAs that players today are unlikely to reach, more than walks. Not putting the ball in play is an issue, but not as much as playing time. Sosa had 150 Ks in his 160 RBI season.