8. Willie McCovey

The Giants already had a popular power hitter in Willie Mays, but no rule in baseball says you can't have two.

Willie McCovey joined the Giants organization as an Amateur Free Agent in 1955, and four years later, he was their Rookie of the Year.  With all due respect to McCovey, the Giants didn't know what they had early in his Major League career.  McCovey was a unique Rookie of the Year winner, as he did not even get called up until July 30, and he won the award against slim pickings with only 219 Plate Appearances, but he had an OPS of 1.085 that year.  Pitcher figured out McCovey in 1960, and his Batting Average dropped below .240, and he was sent to the Minors.  

Over the first few years of the 1960s, McCovey showed power but not consistency, and it looked like he was meant to be an average MLB player, but he broke out in 1963, winning the Home Run Title (44), and going to his first All-Star Game.  After a drop-off in 1064 (18 HR, .220 BA), McCovey roared back, with six consecutive 30-plus Home Run Seasons, leading the NL in 1968 (36) and 1969 (45).  In both seasons, McCovey topped the Senior Circuit in RBIs, Slugging Percentage, and OPS, and he won the coveted MVP in 1969.  He would have his third straight Slugging and OPS Titles in 1970.

McCovey remained a potent slugger into the 1970s, but the struggling Giants traded him to San Diego after the 1973 Season, but returned as a Free Agent as a popular veteran in 1977, concluding his career with San Francisco for four seasons before retiring in 1980.

The slugger blasted 521 Home Runs, 469 with the Giants, while also collecting 1,974 Hits and 1,388 RBI for the team.  The Baseball Hall of Fame inducted McCovey in his first year on the ballot in 1986.  The Giants also retired his number 44 in 1980, and he was chosen for the inaugural class of the Giants Wall of Fame in 2008.