Martinez, 27, only joined Atlanta from River Plate last year and scored 11 goals and provided 16 assists in 54 appearances for the MLS club.

The two-time Argentina international, named an MLS All-Star in 2019, helped Atlanta win the U.S. Open Cup and Campeones Cup last year.

"We want to thank 'Pity' for his contributions to our club for the past two years," Atlanta vice-president and technical director Carlos Bocanegra said. "He will forever be a part of Atlanta United's history after playing an integral part in our 2019 season in which we lifted two trophies.

"We'll look to be diligent in our efforts to fill that roster spot during this window."

Martinez will join an Al-Nassr side that will finish second in the Saudi Professional League in 2019-2020.

Atlanta, meanwhile, sits eighth in the Eastern Conference after three wins from nine in MLS in 2020.