He played college football at Wisconsin, and signed with the San Diego Chargers as an undrafted free agent in 2013.

[1] He was selected to the first-team all-district and all-area team in his senior season in high school.

On April 27, 2013, Cromartie signed with the San Diego Chargers as an undrafted free agent.

[7][8] After cornerbacks Tramaine Brock and Kenneth Acker sustained injuries, Cromartie was promoted to the active roster and made his first start of 2015 on November 8, 2015, against the Falcons, recording seven tackles.

[19] In the first game of the season, Cromartie recorded seven tackles, and recovered a fumble that was forced by teammate Tommie Campbell.

According to Cromartie, a verbal agreement was made on financial terms that would pay Sluka $100,000 to transfer to UNLV, but no money was paid, but Brennan Marion didn’t keep his word.