Nieuwenhuis attended Denver Christian High School in Lakewood, Colorado where he played football, basketball and baseball.

[1] However, Nieuwenhuis feared that he lacked the size to succeed as a football player at the next level and that he would be converted to a wide receiver and made to redshirt as a freshman.

[2] As a high school baseball player, Nieuwenhuis was a lightly recruited second baseman and pitcher whose fastball reached 90 miles per hour.

There he led the Cougars to back-to-back NAIA World Series appearances in 2007 and 2008 and set school career records in runs scored, with 190, and triples, with 12.

[citation needed] Nieuwenhuis began his professional career with the Brooklyn Cyclones in the New York–Penn League, where he played 74 games and hit .277.

Though he garnered early National League Rookie of the Year consideration for his .297 average, six home runs and superlative outfield defense through June 15, Nieuwenhuis batted .123 with one home run after that date, striking out in more than 44 percent of his plate appearances.

[8] On August 6 while with Buffalo, Nieuwenhuis was diagnosed with a partial tear of the plantar fascia in his right foot, which occurred while running down the first-base line just days after being optioned by the Mets.

[9] He reported to Port St. Lucie for rehab, then on August 22, he was shut down for the rest of the season to heal his foot.

When interviewed after his exceptional game that day, Kirk commented in response to his critics: "there's more to life than baseball".

After their third consecutive comeback win the next day, the Mets swept the Nats, moving themselves to 7.0 games ahead in the NL East.

[22] On March 19, 2019, Nieuwenhuis signed with the Long Island Ducks of the independent Atlantic League of Professional Baseball.