Nationals infield prospect Anthony Rendon suffered a badly sprained left ankle last night with Class A Potomac, a team spokesman said. The Nationals need to gather more information and wait for the swelling to go down in Rendon’s ankle before they determine a timetable for his recovery.

Rendon, the sixth overall pick in last year’s draft and the Nationals’ top prospect behind Bryce Harper, hit a double in the fourth inning at Class A Lynchburg. On an ensuing base hit, Rendon tried to score and fell to ground the after rounding third base. He had to be helped off the field, putting no weight on his left leg.

Rendon, 21, has no injury history with his left ankle, but he suffered several health setbacks as an amateur. In 2009, Rendon tore ligaments in his right ankle and in July 2010, while playing for Team USA, he fractured his right ankle. Last year, at Rice, Rendon had to play the majority of his junior season at designated hitter because of a strained muscle behind his shoulder.

Last night, Rendon was playing his second game at Potomac. He began his professional career by going 2 for 4 with a double, a triple and two walks.

Rendon wowed Nationals executives, coaches and teammates this spring with his easy swing and smooth fielding. He played third base, shortstop and second base. He had a chance to earn a call-up at the end of this season, but more than likely would have reached the majors at some point in 2013. It remains to be seen how his most recent injury affects his ascension.