"Scouts and executives from multiple clubs continue to express doubt about the ability of Pirates Triple-A outfielder Starling Marte to become a star. Marte, who turns 24 on Oct. 9, generally draws raves for his defense, but one scout describes him as a "tweener" with shaky instincts in center field and not enough power for left. The scout also says that Marte struggles with good fastballs and too frequently is caught stealing; Marte has succeeded in only 18 of 30 attempts, or 60 percent. Marte has improved his walk rate this season and still has time of develop. But at this point, it seems unlikely that he could be the centerpiece of a trade for a player such as Diamondbacks right fielder Justin Upton."