Koo was on the Patriots' practice squad. In 2017, he played in four games and was 3-of-6 on field goals, including 1-of-4 from 40 to 49 yards. He's never attempted a kick beyond 50 yards in the NFL.
Koo was the kicker on the Atlanta Legends, during their short-lived Alliance of American Football season. He was a perfect 14-of-14 on his attempts, his longest at 38 yards.
Koo is the fourth NFL player born in South Korea.
In college, he was an All-Sun Belt selection and a finalist for the Lou Groza Award.
Meanwhile, the Falcons waived quarterback Danny Etling and cornerback D.J. White on Monday.
