As the comment on the back indicates, Lemon wasn't the team's manager. After finishing last in his only season as a skipper, THREE MONTHS LATER he was canned in favor of Ted Williams, who has a card later in the set.
I'm wondering why, if Topps knew about his firing (to be able to add the note on the back), why did they even include a card for him? Why not pull it and replace it with, oh I don't know, maybe a SENATORS ROOKIE STARS CARD?
Prior to managing, Lemon was an outfielder for the (old) Senators and Twins, which you can read about here. He was also a coach for the Twins from 1965-67, and 1981-84.
Lemon passed away in 2006 at age 78.