Jun 17, 2019; Omaha, NE, USA; Texas Tech Red Raiders pitcher John McMillon (17) pitches in the ninth inning against the Arkansas Razorbacks in the 2019 College World Series at TD Ameritrade Park. Mandatory Credit: Steven Branscombe-USA TODAY Sports

Kansas City Royals relief prospect John McMillon has completed the most improbable of journeys through the minor league system.

The Royals announced Wednesday afternoon that they have selected the contract of the 25-year-old right-hander from Double-A Northwest Arkansas. McMillon began the season with Low-A Columbia and has pitched for three different Royals affiliates this season. To make room for him on the 26-man active roster, right-hander Nick Wittgren was optioned to Triple-A Omaha, and to clear space for him on the 40-man roster, righty Brad Keller was transferred to the 60-day injured list.

McMillon, who is nicknamed "The Whammer" due to his resemblance to the character in the 1984 film "The Natural," was signed as an undrafted free agent out of Texas Tech following the abbreviated 2020 draft. After struggling mightily through his first two professional seasons, McMillon put it all together this year. He held opponents to a .108 batting average and a 3.38 ERA over 10.2 appearances with Columbia and quickly received a promotion to High-A Quad Cities, where he posted a 2.70 ERA with a .119 opponent average. He has allowed only two earned runs over 20.2 innings in Double-A — good for a 0.87 ERA — and has limited opposing hitters to a .171 average. McMillon's ability to miss bats — he has an incredible 91 strikeouts over 51.1 innings this season — allowed him to make a meteoric rise through the system, despite the fact that he seemed to be fighting for his career just one year ago.

Wittgren, who had to consent to being optioned to the minors since he has more than five years of major league service time, had a 4.97 ERA with a 1.41 WHIP in 29 major league innings this season.

Keller's transferral to the 60-day IL is purely procedural, as he's been out of action since May 15 and could be activated at any point. Keller, who has been battling right shoulder impingement syndrome, was shut down a couple weeks ago after a month-long rehab assignment with Triple-A Omaha, but he returned to the mound Monday with the Royals' Arizona Complex League affiliate, allowing three earned runs in a third of an inning.