Central Notes: Pirates, Royals, Cubs

With 40% of their innings coming from relievers, the Pirates' bullpen has been worked the hardest among all National League teams.  The onus is on GM Neal Huntington to add depth at the trade deadline, writes Jon Paul Morosi of FOX Sports, who notes that the NL Central is "tougher than many of us expected" due to the Pirates playing .591 ball so far.  Elsewhere in baseball's central divisions…

• The Royals are the frontrunner to sign 15-year-old Italian shortstop Marten Gasparini, sources tell Ben Badler of Baseball America, with the Dodgers and Cubs also showing interest.  Gasparini, who turns 16 on Friday, is "expected to sign the biggest contract ever for a European amateur player," according to Badler.  The speedy switch-hitter may top the $800K the Twins gave to German outfielder Max Kepler in 2009.  Be sure to check out Badler's full profile of Gasparini.
• Josh Vitters is the future at third base for the Cubs, president Theo Epstein told Ian Stewart, Stewart explained to MLB.com's Carrie Muskat.  That means playing time will be hard to come by for Stewart at Triple-A Iowa, where he landed after being removed from the Cubs' 40-man roster this month.  Stewart wondered if the comment was Epstein's way of trying to get him to give up his contract, but the third baseman told Muskat, "It wouldn't really make sense for me to take a release or ask for free agency, because then I'd be giving up my contract, and that doesn't make sense for me financially or for my family."  Stewart signed a $2MM deal to remain with the Cubs after being non-tendered in December, and hoped to be with the big league club after rehabbing a February quad injury.
• Matt Garza will make his season debut tomorrow with the Cubs in Pittsburgh, and he's eligible for free agency after the season.  Jesse Rogers and Bruce Levine of ESPNChicago.com discussed Garza's future, with Levine suggesting, "I believe if he stays healthy the Cubs will offer him a short-term extension that could be a plus for both sides."
• The Twins "will get a close approximation of what it would be like to have Mike Trout and Bryce Harper in the same lineup" when top prospects Byron Buxton and Miguel Sano reach their primes, writes Jim Callis of Baseball America.  Asked to rank prospect tandems in terms of potential five years down the road, Callis ranked Buxton and Sano ahead of Oscar Taveras and Shelby Miller of the Cardinals, Jose Fernandez and Christian Yelich of the Marlins, and Dylan Bundy and Manny Machado of the Orioles, among others.