For fans in the cities that aren’t absorbed in a playoff race, September brings the exciting call-up: the cup of coffee for that minor league stud who – cross your fingers – will be a big part of the team’s future. Not every call-up becomes a star, or even a major league regular, but the following four players have incredible potential and it’ll be surprising if any of them don’t have a major impact on the 2006 season.

JEREMY HERMIDA, MARLINS Hermida was selected 11th overall in the 2002 amateur draft, ahead of now-established major leaguers like Scott Kazmir and Khalil Greene. Many regarded the young outfielder as the best pure high school hitter in the draft, which is saying a lot considering Tampa’s B.J. Upton and Atlanta’s Jeff Francoeur were both picked that year.

At the end of his first two years in the minor leagues, though, some were beginning to wonder when Hermida’s power would arrive. At Greensboro in the Single-A South Atlantic League in 2004, he hit only six home runs in 133 games on his way to a .284 AVG/.387 OBA/.393 SLG season. The numbers were impressive for that league, but not as explosive as many had been expecting.

The hope was always that Hermida’s lightning-fast stroke from the left-hand side would give him light-tower power once he added bulk to his frame and more uppercut to his swing. Those hopes were rewarded in 2005. In Double-A this year, Hermida put together a .293/.453/.518 season with 18 home runs and 49 extra-base hits in 118 games.

Still just 21, he can hit for contact, hit for power, control the strike zone (111 walks in the minors this year), play a decent right field, and steal a base (23 stolen bases with a 92% success rate in 2005).Other clubs certainly noticed Hermida’s breakout season: He was mentioned in nearly every trade negotiation the Marlins had at the deadline, and the team’s refusal to part with him was one of the reasons the Marlins were unable to consummate any big deals.

Hermida has struggled a bit in his first month in the majors, but he ought to be ready to replace Juan Encarnacion in right field next season. With Hermida in one corner and Miguel Cabrera in the other, the Marlins will have a vicious young twosome to hit in the middle of their lineup.

FRANCISCO LIRIANO, TWINS One of the filthiest pitchers in the minor leagues this year, this left-hander’s high three-quarters delivery from the left side and small stature – he checks in at 6-foot-2 and 185 pounds – have led many scouts to compare him to Minnesota ace Johan Santana.

Liriano mixes a fastball that tops out at 97 mph with a hard-breaking slider at 86-88 mph and a strong change-up. He can work his fastball to either side of the plate, and when he locates that pitch, the results are devastating (the 204 strikeouts Liriano notched in 167.2 innings led all minor leaguers this year). Liriano’s control is so sharp that he only gave up 50 walks in those 167.2 innings. His breaking ball and off-speed pitch are so good that some scouts think the fastball might end up being his weakest offering.

The concern with Liriano has always been his health; he was shut down for almost all of 2003 with shoulder problems, which is why the Giants were willing to package him with Joe Nathan for one year of A.J. Pierzynski. Giants GM Brian Sabean is certainly regretting that deal (one of his few trade gaffes), and Twins GM Terry Ryan is riding Liriano all the way into next year’s rotation. Starter Joe Mays has an $8.5 million team option for next season and, with Liriano in the wings, there is no chance the Twins will pick up his contract.

RYAN ZIMMERMAN, NATIONALS Zimmerman was picked fourth overall this June in the amateur draft, and he quickly rocketed through the minor leagues, hitting .471/.472/1.059 in four games at Single-A and .326/.371/.528 in 63 games at Double-A. The impressive slugging average was especially heartening for the Nationals’ front office since Zimmerman only began to show a capacity for hitting the long ball during a summer stint with Team USA. At the University of Virginia, Zimmerman hit a home run every 100 at-bats; in the minors this year, he averaged one round-tripper every 22 at-bats.

Zimmerman has absolutely tattooed the ball in the majors this year, posting a stat line of .438/.424/.625 in 14 games with the Nationals so far. Perhaps the most exciting thing about Zimmerman, however, is his defense.

At third base, he rates as an extraordinary defender by any metric. His hands, range, and arm are so impressive that both the University of Virginia and the Washington Nationals have messed around with him at shortstop. Moving him there permanently is hard to imagine – the hulking kid will turn 21 next week, but already checks in at 6-foot-3 and 220 pounds – but it just goes to show how strong his defense is. Baseball America reported that one scout’s only question about Zimmerman was how many gold gloves he’d win.

Mr. Gorman is a writer for Baseball Prospectus. For more state of the art commentary, visit baseballprospectus.com.