The Baltimore Orioles are unlikely to promote top prospect Ryan Mountcastle as a September call up this month, according to a report.

Mountcastle was the 35th overall pick in 2015 (supplemental round) and ranks among the club's top five prospects.

He is hitting .310/.343/.527 with 25 homers, 35 doubles and one triple through 548 plate appearances in Triple-A.

His defense is considered an issue and some scouts believe he lacks a true defensive position.