Hedges, 19, is hitting .266 with five home runs and 25 runs batted in. The backstop, selected in the second round of the 2011 draft by the San Diego Padres, has started 36 games behind the plate this season.
Peterson, 22, is hitting .304 with one home run and 17 runs batted in. His 18 stolen bases are tied for fifth in the league, and his .399 on-base percentage is fifth best in the 16-team circuit. The McNeese State product was the 58th overall pick in the 2011 draft.
Portillo, 20, is 4-2 with a 1.66 ERA in 11 starts. His earned run average is the best among starters in the league. The righthander is holding opposing batters to a .165 batting average, good for third best in the league. The Venezuelan-born hurler was named the Midwest League Pitcher of the Week for May 21st to May 27th.
Garces, 22, is 1-3 with a 2.73 ERA. The lefty, who made his U.S. debut on April 5th against Lake County, has struck out 52 batters in 56 innings of work.
The All-Star game will take place at Fifth Third Bank Ballpark, the home of the Kane County Cougars in Geneva, Illinois.