Marcos will make his first ATP Challenger Tour appearance of the year in Saint-Brieuc, where he is the top seed.
Making his debut at the Open Harmonie Mutuelle, a €43,000 event in the northwest corner of France, Marcos will open against Italy's Andrea Arnaboldi. It will be their first meeting.
Marcos is seeking to carry his strong run of form from the ATP World Tour Masters 1000 event in Indian Wells, where he reached the Round of 16 as a qualifier. Now, back inside the Top 100 at No. 82, he is on the way up the ATP Rankings.
Other players in Saint-Brieuc include second seed Ricardas Berankis, Lukas Lacko, Sergiy Stakhovsky and Elias Ymer. A potential quarter-final against Ymer awaits, with Stakhovsky looming in the semis.