O'Neill is out of the lineup for Friday's game against the Rays, Jake Rill of MLB.com reports.
O'Neill was also on the bench for the final game before the All-Star break and has gone 3-for-22 in six contests since returning from the injured list in early July. The veteran outfielder has struggled to a .585 OPS in his first 30 games for Baltimore after inking a one-year, $16.5 million contract in December.