The Diamondbacks requested that any trade offer include Starlin Castro. Trade discussions were then cut off.
Upton made his MLB debut in 2007. His career numbers include a .832 on-base-plus slugging percentage (OPS), .278 batting average, 363 RBIs, 108 home runs and 80 stolen bases. His 2012 numbers include a .785 OPS, .280 batting average, 67 RBIs, 17 home runs and 18 stolen bases.
Let’s compare that to Castro, who debuted in 2010. His career numbers include a .761 OPS, .297 batting average, 185 RBIs, 27 home runs and 57 stolen bases. His 2012 numbers include a .753 OPS, .283 batting average, 78 RBIs, 14 home runs and 25 stolen bases.
Wins above replacement scores (WAR) are a sabermetric statistic that tries to show how valuable a player is on his team. Upton has scored lower than 2.2 in two of his last three seasons. Castro scored 3.0 in 2011. He scored 3.4 in 2012. Those numbers should improve as he eliminates errors, and improves his power-hitting stroke.
Another advantage with Castro is that he plays shortstop. Shortstops who can hit well are much scarcer than outfielders. Alfonso Soriano is an example of a player who, while horrible on defense, was moved to the outfield because of his powerful bat.
Upton could help the Cubs, but not at the expense of Castro. Castro is younger, more durable, produces at a position of scarcity, and he has a longer contract. Furthermore, Upton supposedly has four teams that he can veto any trade to, and the Cubs are one of those teams. Why try to acquire a player who doesn’t want to join the franchise?