Whether or not the Cubs add a high-octane reliever before the July 31 trade deadline, Dillon Maples is lurking as an X-factor in the second half for the defending World Series champs.

The Cubs are planning to promote Maples to Triple-A Iowa, sources said Monday, after the right-hander blew away hitters at Double-A Tennessee, pitching backwards and unleashing a wipeout slider to notch 28 strikeouts in 13.2 innings.

Maples had never pitched above the A-ball level until this season, putting up a 5.33 career ERA and staying far off the radar after getting a $2.5 million bonus as a 14th-round pick in the 2011 draft, the last one overseen by former general manager Jim Hendry.

That’s when chairman Tom Ricketts wisely authorized a spending spree before a new collective bargaining agreement would radically change the spending limits on amateur talent. Ricketts fired Hendry in a secret meeting that summer, but asked him to stay on and close a draft class headlined by Javier Baez.

Maples – Gatorade’s North Carolina high school player of the year – had options as a punter/kicker with a football scholarship to the University of North Carolina. While that athleticism hasn’t translated into the frontline starter the Cubs once envisioned – Maples has dealt with injuries and thrown only 182.1 innings across the last five seasons combined – something clicked out of the bullpen this year.

The Cubs see Maples as having an 80 slider on the 20-80 scouting scale and encouraged him to use that as his primary weapon, understanding there will still be a learning curve in the Pacific Coast League.

Maples also gave up 11 hits and 11 walks in those 13.2 innings with the Smokies after a strong showing at advanced Class-A Myrtle Beach (4-0, 2.01 ERA, 44 strikeouts in 31.1 innings).

That’s probably not where Maples envisioned beginning his age-25 season. And Joe Maddon’s bullpen – with All-Star closer Wade Davis and setup guys Carl Edwards Jr., Koji Uehara and Pedro Strop – has been a real strength for a 46-45 team. But all these years later, Maples will soon be one phone call away from Wrigley Field.