Seitzer batted .318 over four minor league seasons and facilitated the Royals’ move of George Brett. Seitzer would have been a certain Rookie of the Year in most seasons, but in 1987, Mark McGwire hit 49 home runs and Seitzer settled for second. He led the AL in hits, and was only the 13th rookie in history to collect 200. Seitzer had good speed, and although not known for power in the minors, he muscled up for 15 home runs and 83 RBI his first full season. A good batting eye enabled him to draw numerous walks, keeping his on-base percentage near .400. With Kurt Stillwell joining Seitzer in 1988, the Royals had a young, exciting, and productive left side of the infield. His finest game came August 1, 1987, when he clobbered Red Sox pitching for six hits and seven RBI.
Seitzer spent the better part of five seasons with the Royals, but his batting average steadily declined from his standout rookie campaign. The Royals released him late in spring training 1992, and he was picked up by the Milwaukee Brewers eight days later. He successfully revitalized his career with the Brewers, batting over .300 from 1994 through 1996, and made his second All-Star team in 1995.
Seitzer was dealt to the Cleveland Indians mid-1996 for Jeromy Burnitz, and batted .386 down the stretch for them, helping them into the playoffs. However, he received limited playing time in the postseason in both 1996 and 1997. Despite offers to re-sign with Cleveland and play for other teams, he chose to retire after the 1997 season, leaving the game with a solid .295 lifetime batting average.