Austin Riley is projected by Baseball America to be Atlanta’s third baseman by 2020. The former DeSoto Central High star has climbed the minor-league ladder at a good pace, reaching the Double-A level midway through his third pro season at age 20. He’ll make his much-anticipated Trustmark Park debut on Wednesday as the Mississippi Braves open a 10-game homestand during which Riley will have a chance to display the power bat and rifle arm that enticed the Braves to draft him 41st overall in 2015. Riley, 6 feet 3, 220 pounds, is 4-for-18 for the M-Braves to date; he hit his first Double-A homer on Monday at Pensacola. He doesn’t arrive in Pearl with quite the same pizzazz that accompanied Ronald Acuna, but Riley is rated among the top 18 prospects in Atlanta’s loaded system by three different publications. He has already had a decorated minor league career, making Baseball America’s rookie-level All-Star team in 2015 and low Class A team in 2016. He was a midseason All-Star pick in the high-A Florida State League last month and was batting .252 with 12 homers for Florida at the time of his promotion. MLB Pipeline’s scouting report notes that Riley, like many young sluggers, needs to be more selective at the plate, cut down on strikeouts and draw more walks. But his raw power excites, and how that tool plays at Trustmark Park will be something to watch for. … Riley, who was born in Memphis but grew up in Southaven, joins the list of Mississippians to play for the M-Braves that includes Zack Bird, Jay Powell, Michael Rosamond, John Thomson, Van Pope and Brent Leach.