Double-A Binghamton placed Serrano on the 7-day injured list with a shoulder strain in mid-June, Matt Eddy of Baseball America.
Serrano, who last played June 13, could be back before the end of July, per Eddy's report. The 23-year-old outfielder has struggled in his first season at Double-A, slashing .193/.304/.339 with three home runs, six steals and a 26 percent strikeout rate in 54 games.