Cilic picked up the ninth ATP title of his career by winning the PBZ Zagreb Indoors last year in his home country. He also won the event in 2009 and '10. He started his defense Monday with a 6-4, 6-4 win over Mate Delic, a fellow Croat.
Cilic, the No. 5 seed this year, dropped just nine points over 10 games serving, winning on serve at an 82 percent rate. He was able to cash in two of his five break opportunities.
The other main draw match Monday saw Benjamin Becker get by Jesse Huta Galung 7-6 (4-7), 6-4, 7-6 (8-6). Becker ended up with one break in each set and need the one in the third set to force the final tiebreaker.
Becker earned a second-round slot opposite top-seeded Tommy Haas.